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Molecular beam measurements of nuclear moments before magnetic resonance. Part I: I. I. Rabi and deflecting magnets to 1938

Paul Forman Smithsonian Institution, Washington, DC, 20560, USA
Pages 111-160 | Received 03 Jul 1997, Published online: 18 Sep 2006

  • The autobiographical sources for Rabi consulted are listed in chronological order, and are cited in the notes as ‘Rabi (date), pp. of transcript or publication’. Rabi (1962–3), five interviews for the Columbia University Oral History Research Office, November 1962-March 1963, by Barbara Land and Morris Krieger, transcript, continuously paginated, 130pp.; Rabi (December 1963), interview for Sources for History of Quantum Physics, 8 December 1963, by Thomas S. Kuhn, transcript, 33pp., in Archive for History of Quantum Physics; Rabi (13 October 1975) and Rabi (20 October 1975): Bernstein Jeremy Physicist The New Yorker 1975 October 47 110 13 and (20 October 1975), 47–101 (quotation and paraphrase of interviews); Rabi (1978): Daniel J. Kevles, The Physicists: The History of a Scientific Community in Modern America (New York, 1978; reissued, with a new preface, Cambridge, Mass., 1995), 213–5 (‘based on interviews with I. I. Rabi’); Rabi (1983–5), 42 interviews for the Columbia University Oral History Research Office, 1983–5, by Chauncey Olinger, transcript, continuously paginated, 1102pp.; Rabi (16 December 1983): I. I. Rabi, Edward M. Purcell, Edwin H. Land, Jerrold R. Zacharias, and Richard L. Garwin, with Jack S. Goldstein, moderator, ‘Scientists as Citizens’, recollections and discussions videotaped at Brandeis University, 16 December 1983, transcript, 57pp., and videotapes in Zacharias Papers, MIT Archives; Rabi (13 February 1984), interview, 13 February 1984, by S.S. Schweber, transcript, 25pp., in Niels Bohr Library, American Institute of Physics; Rabi (29 March 1984): I. I. Rabi, Julian S. Schwinger, Norman F. Ramsey, Sidney Millman, and Jerrold Zacharias, with Jack S. Goldstein, moderator, ‘Reminiscences of the thirties’, recollections and discussions videotaped at Brandeis University, 29 March 1984, transcript, 57pp., and videotapes in Zacharias Papers, MIT Archives; Rabi (15 November 1985): I. I. Rabi, Jerrold R. Zacharias, Edward M. Purcell, Robert B. Palmer, Julian S. Schwinger, and Victor F. Weisskopf, with Jack S. Goldstein, moderator, ‘Talking about Science’, discussions videotaped at Brandeis University, 15 November 1985, transcript, 54pp., and videotapes in Zacharias Papers, MIT Archives; Rabi (1988): I. I. Rabi, as told to John Rigden, ‘Otto Stern and the discovery of space quantization’, Zeitschrift für Physik, D10 (1988), 119–20. I have not seen the following sources cited by J. S. Rigden (note 5, 1987), nn.1 and 16 to chapter 1: ‘I. I. Rabi, interview by Edwin Newman, December 1972, transcript, William E. Wiener Oral History Library, New York’ and ‘I. I. Rabi, interview by Stephen White, 11 February 1980, transcript, Rabi private collection’.
  • Rabi to F. K. Richtmyer January 1929 22 draft (Library of Congress, Rabi Papers, box 7, folder 7)
  • The most complete collection of references to pre-Second World War molecular beam research is Bessey W.H. Simpson O.C. Recent Work in Molecular Beams Chemical Reviews 1942 30 239 279 For the magnetic resonance technique, as also for valuable discussions and references on earlier techniques, see Norman F. Ramsey, Molecular Beams (Oxford, 1956; repr. 1990); Polykarp Kusch and Vernon W. Hughes, ‘Atomic and molecular beam spectroscopy’, Handbuch der Physik/Encyclopedia of Physics, ed. S. Flügge (Berlin, 1959), vol. 37, pt. 1, 1–172. Specifically historical are Ramsey, interviews for Columbia University Oral History Research Office, July and August 1960, by Joan Safford, transcript, 358pp., available also at Niels Bohr Library, American Institute of Physics; Ramsey, ‘Early history of magnetic resonance’, Bulletin of Magnetic Resonance (Quarterly Journal of the International Society of Magnetic Resonance), 7 (1985), 94–9; Ramsey, ‘I. I. Rabi’, Physics Today (October 1988), 82, 84, 86; Ramsey, ‘I. I. Rabi, 1898–1988’, National Academy of Sciences of the USA Biographical Memoirs, 62 (1993), 310–24; Ramsey, ‘Origins of magnetic resonance’, in Encyclopedia of Magnetic Resonance (1996), I, 565–9; John S. Rigden, ‘The birth of the magnetic resonance method’, in Observation, Experiment, and Hypothesis in Modern Physical Science, eds P. Achinstein and O. Hannaway (Cambridge, Mass., 1985), 205–37; P. Forman, ‘“Swords into Ploughshares”: Breaking New Ground with Radar Hardware and Technique in Physical Research after World War II’, Reviews of Modern Physics, 67 (1995), 397–455 (404–7, 425–8).
  • Rigden , John S. 1987 . Rabi: Scientist and Citizen 60 – 106 . New York Rigden's scholarly study of ‘Molecular Beam Experiments on the Hydrogens during the 1930s’, Historical Studies in the Physical Sciences, 13 (1983), 335–73, moves very quickly through Rabi's pre-1938 techniques to concentrate on the post-1937 magnetic resonance investigations.
  • Stern to Landé, 1 March 1919 (SHQP microfilm 4) Forman P. Alfred Landé and the Anomalous Zeeman Effect, 1919–1921 Historical Studies in the Physical Sciences 1970 2 153 261 (158–9)
  • Segrè , Emilio and Stern , Otto . 1973 . National Academy of Sciences of the USA . Biographical Memoirs , 43 : 214 – 236 . is the most complete biographical memoir. Also I. I. Rabi, ‘Otto Stern (obituary)’, Physics Today (October 1969), 103–4; Immanuel Estermann, ‘Molecular Beam Research in Hamburg, 1922–33’, in Recent Research in Molecular Beams: A Collection of Papers Dedicated to Otto Stern …, ed. I. Estermann (New York, 1959), 1–7; Estermann, ‘Otto Stern’, Dictionary of Scientific Biography (New York, 1976), xiii, 40–3; Estermann, ‘History of Molecular Beam Research: Personal Reminiscences of the Important Evolutionary Period 1919–1933’, American Journal of Physics, 43 (1975), 661–71; Wolfgang Walter, ‘Otto Stern: Leistung und Schicksal’, in Hochschulalltag im ‘Dritten Reich’: Die Hamburger Universität 1933–1945, eds Eckart Krause et al. (Berlin and Hamburg, 1991), 1141–54, being a slightly expanded version of Walter, ‘Otto Stern: Leistung und Schicksal’, Gesellschaft Deutscher Chemiker, Fachgruppe Geschichte der Chemie, Mitteilungen, no. 3 (1989), 69–82. Dudley Herschbach, guest editor, ‘In Memoriam Otto Stern on the 100th Anniversary of His Birth’, Zeitschrift für Physik, D10, no. 2/3 (November 1988), is a festschrift in which most articles have a historical component. Bretislav Friedrich and Dudley Herschbach, ‘Space Quantization: Otto Stern's Lucky Star’, Daedalus, 127, nr 1 (Winter 1998), 165–91, appeared while this paper was in proof.
  • Stern , Otto . November 1961 . Interview by Res Jost, in Zurich November , 25 and 2 December transcript, 47pp. plus 1p. notes by Jost (ETH Bibliothek, Wissenschaftshistorische Sammlung), where (p. 14) Stern describes himself confronting the Bohr theory in 1914 as an amateur who had come over to theoretical physics from chemistry.
  • Forman , P. , Heilbron , J.L. and Weart , S.R. 1975 . “ Historical Studies in the Physical Sciences ” . In Physics Circa 1900: Personnel, Funding, and Productivity of the Academic Establishments Vol. 5 , 30 – 122 . Princeton Physikalischer Verein zu Frankfurt am Main, Jahresbericht (1915–16), 130; (1916–17), 87. Heinz Fricke, 150 Jahre Physikalischer Verein Frankfurt a.M. (Frankfurt a.M., 1974), 164–6. P. Forman, ‘The Environment and Practice of Atomic Physics in Weimar Germany’, PhD dissertation, University of California, Berkeley, 1967; University Microfilms, 1968.
  • References given by Segrè National Academy of Sciences of the USA Biographical Memoris 1973 43 214 236 ‘Otto Stern’, NAS, Biogr. Mem.
  • Stern , Otto . 1920 . Eine direkte Messung der thermischen Molekulargeschwindigkeit . Zeitschrift für Physik , 2 : 49 – 56 . N. F. Ramsey, ‘Oscillations in the History of Molecular Beams’, in Electronic and Atomic Collisions, eds D. C. Lorents, W. E. Meyerhof, and J. R. Peterson (Amsterdam, 1986), 3–12, points out exactly this predominant initial interest of molecular beamists in kinetic theory and molecular properties, without however connecting the circumstance with their being predominantly physical chemists. Stern, in his 1961 interview by Jost (note 9) recalled (pp. 10–11) that as late as 1913 there were still a great many opponents of the molecular theory among the physical chemists, and cited specifically Emil Baur, the professor of physical chemistry at the ETH. For the tradition of scepticism about atoms, among physical chemists especially, see John W. Servos, Physical Chemistry from Ostwald to Pauling: The Making of a Science in America (Princeton, 1990); Mary Jo Nye, From Chemical Philosophy to Theoretical Chemistry: Dynamics of Matter and Dynamics of Disciplines (Berkeley, 1993), and Molecular Reality: A Perspective on the Scientific Work of Jean Perrin (London and New York, 1972).
  • Stern , Otto . 1921 . Ein Weg zur experimentellen Prüfung der Richtungsquantelung im Magnetfeld . Zeitschrift für Physik , 7 : 249 – 253 .
  • Stern himself, in proposing Ein Weg 1921 7 249 253 says for literature see Arnold Sommerfeld, Atombau und Spektrallinien, 2nd edn (Braunschweig, 1921). There was at that time some disagreement among quantum theorists about exactly how many orientations were allowed
  • At issue here is a double refraction induced by application of a magnetic field but independent of the strength of the applied field, with the gas or vapour behaving like a uniaxial crystal (e.g. the calcite form of calcium carbonate), the direction of the magnetic field being that of the crystal axis. Stern was the first to point out that such behaviour seemed to follow from space quantization of planar electron orbits. The double refraction here at issue is not to be confused with the double refraction transverse to the magnetic field found in 1912 in sodium vapour by W. Voigt (with the collaboration of Bohr's school friend and informant H. M. Hansen), nor with the Cotton-Mouton effect — proportional to H2 — wherein otherwise isotropic liquids behave like uniaxial crystals in a magnetic field. See Ingersoll L.R. Magneto-Optics Theories of Magnetism et al. 1922 3 251 261 National Research Council, Bulletin, no. 18 (= vol. 3), pt W. Gerlach, ‘Das magnetische Verhalten von Gasen und Dämpfen’, in Atti del Congresso Internazionale dei Fisici, 11–20 Settembre 1927, Como-Pavia-Roma (Bologna, 1928), I, 77–94; Wilhelm Schütz, Magnetooptik (ohne Zeeman-Effekt) (Leipzig, 1936) (= Handbuch der Experimentalphysik, eds W. Wien and F. Harms, vol. 16, pt I), 213; Terry Shinn, ‘The Bellevue Grand Électroaimant, 1900–1940: Birth of a Research-Technology Community’, Historical Studies in the Physical Sciences, 24 (1993), 157–87. The conceptual importance for Stern of the absence of this magnetically induced double refraction that the Bohr model seemed to demand is indicated by his mentioning it not only in ‘Ein Weg’ (note 13) as motivation for the magnetic deflection experiment, but also again, 25 years later, stressing in his (brief and undetailed) Nobel lecture ‘the contradiction with respect to the double refraction’ that the result of the experiment seemed to present. Stern, ‘The Method of Molecular Rays, Nobel Lecture, December 12, 1946’, as reprinted in Nobel Lectures Including Presentation Speeches and Laureates' Biographies: Physics, 1942–1962, ed. Nobelstiftelsen (Amsterdam, 1964), 8–16 (11–12). Both Walther Gerlach and Immanuel Estermann recalled in the interviews they gave to Sources for History of Quantum Physics that during the Easter vacation 1922, i.e. almost immediately following the ‘success’ of the Stern-Gerlach experiment, they, together with Stern, tried hard for some weeks to find the requisite optical birefringence of Na (in lieu of H). W. Gerlach, interview for SHQP, February 1963, by T. S. Kuhn, transcript, 57pp. in AHQP (14–15); I. Estermann, interview for SHQP, December 1962, by J. L. Heilbron, transcript, 24pp. in AHQP (4–6). Although this failure was not reported directly, Gerlach, who put his student Wilhelm Schütz, PhD dissertation, Frankfurt, 1923, on the problem, did say in print, ‘Magnetismus und Atombau’, Ergebnisse der exakten Naturwissenschaften, 2 (1923), 124–46 (142), that if space quantization really occurs in the sense of a ‘fixed alignment of the angular momentum axis in the direction of the magnetic field, then a gas or a metal vapour ought to be anisotropic, double-refracting in a magnetic field: thus far this effect cannot be observed’. Gerlach rightly associated the absence of this effect with ‘the still obscure connection between dispersion and the quantum theory’.
  • Weiss , Pierre . 1911 . Über rationalen Verhältnisse der magnetischen Momente der Moleküle and das Magneton . Physikalische Zeitschrift , 12 : 935 – 952 . Otto Stern, ‘Zur Molekulartheorie des Paramagnetismus fester Salze’, Zeitschrift für Physik, 1 (1920), 147–53. Pierre Quédec, ‘Weiss’ Magneton: The Sin of Pride or a Venial Mistake?’, Historical Studies in the Physical Sciences, 18 (1988), 349–75; Stephen T. Keith and Pierre Quédec, ‘Magnetism and Magnetic Materials’, in Out of the Crystal Maze: Chapters from the History of Solid-State Physics, eds Lillian Hoddeson et al. (Oxford, 1992), 359–442.
  • Gerlach (note 18), … 1927, Como, 87; Van Vleck J.H. The Theory of Electric and Magnetic Susceptibilities Oxford 1932 V 105 121 ‘Susceptibilities in the Old Quantum Theory, Contrasted with the New’. See also the discussion of the Glaser effect in section 3.
  • Physikalischer Verein zu Frankfurt am Main, Jahresbericht (1919/20–1924/25), 35. Forman (note 10), Diss., 232. Born Gerlach Die Zerstreuung des Lichtes in Gasen Zeitschrift für Physik 1921 5 374 375 Born and Gerlach, ‘Elektronenaffinität und Gittertheorie’, Zeitschrift für Physik, 5 (1921), 433–41. Both papers were submitted in the spring of 1921 as Born was moving from Frankfurt to Göttingen.
  • Gerlach , Walther and Stern , Otto . 1921 . Der experimentelle Nachweis des magnetischen Moments des Silberatoms . Zeitschrift für Physik , 8 : 110 – 111 . received 18 November 1921; idem., ‘Der experimentelle Nachweis der Richtungsquantelung im Magnetfeld’, Zeitschrift für Physik, 9 (1922), 349–52, received 1 March 1922; idem., ‘Das magnetische Moment des Silberatoms’, ibid., 353–5, received 1 April 1922. Rarely cited, but of particular interest in this connection, is the talk that Gerlach gave on that same date, 1 April, in the Nederlandische Natuurkundige Vereeniging, reported with the following discussion as Walther Gerlach, ‘Der experimentelle Nachweis der Richtungsquantelung im Magnetfeld und das magnetische Moment des Silberatoms’, Physica, 2 (1922), 122–7. See also Wolfgang Pauli, Wissenschaftlicher Briefwechsel mit Bohr, Einstein, Heisenberg u.a., vol I: 1919–1929, ed. … K. v. Meyenn (New York, 1979), 54–5.
  • 1919/20–1924/25 . Physikalischer Verein zu Frankfurt am Main . Jahresbericht , : 111 – 111 . W. Gerlach and O. Stern, ‘Über die Richtungsquantelung im Magnetfeld’, Annalen der Physik, 74 (1924), 673–99 and plt. III; W. Gerlach, ‘Über die Richtungsquantelung im Magnetfeld II. Experimentelle Untersuchungen über das Verhalten normaler Atome unter magnetischer Kraftwirkung’, Annalen der Physik, 76 (1925), 163–97 and plts IV and V; further, although not concerned with deflection but only detection, W. Gerlach, ‘Atomstrahlen’, Ergebnisse der exakten Naturwissenschaften, 3 (1924), 182–98.
  • Stern , Otto . 1926 . Zur Methode der Molekularstrahlen (Untersuchungen zur Molekularstrahlmethode, Nr. 1) . Zeitschrift für Physik , 39 : 751 – 763 . F. Knauer and O. Stern, ‘Zur Methode der Molekularstrahlen. II (Untersuchungen zur Molekularstrahlmethode, Nr. 2)’, Zeitschrift für Physik, 39 (1926), 764–79. For Stern at Hamburg, see the papers by Estermann, Herschbach, Rabi, Segrè, and Walter cited in note 8.
  • The U.z.M. are listed by Estermann (note 8), ‘Hamburg, 1922–1933’ (1959), 7. On the ‘progressive’ character of the Zeitschrift für Physik: Forman P. The Financial Support and Political Alignment of Physicists in Weimar Germany Minerva 1974 12 39 66 Frank Holl, ‘Produktion und Distribution wissenschaftlicher Literatur: Der Physiker Max Born und sein Verleger Ferdinand Springer 1913–1970’, Archiv für Geschichte des Buchwesens, 45 (1996), 1–225 (130–4).
  • Stern . 1926 . Zur Methode der Molekularstrahlen (Untersuchungen zur Molekularstrahlmethode, Nr.1) . Zeitschrift für Physik , 39 : 751 – 763 . U.z.M. Nr. 1, 759–763. (Gerlach, the physicist, insisted on speaking of Atomstrahlen.) Perhaps the best testimony to Stern's continuing identification — and acquaintance — with physical chemistry is his preparing, together with Georg v. Hevesy, a systematic, comprehensive, topic-by-topic survey of Fritz Haber's scientific work for the issue of Die Naturwissenschaften in Haber's honour: Hevesy and Stern, ‘Fritz Habers Arbeiten auf dem Gebiete der physikalischen Chemie und Elektrochemie’, Naturwissenschaften, 16 (1928), 1062–8. Keith J. Laidler, The World of Physical Chemistry (Oxford, 1995), 229, cites Stern for the Stern-Gerlach experiment and for his 1924 contribution to the theory of charge layers at the surface of electrolytic electrodes, but attaches to him the epithet ‘physicist’.
  • Cf. Estermann National Academy of Sciences of the USA Biographical Memoirs 1973 43 214 236 ‘Hamburg 1922–1933’ (1959), 2.
  • Rosenfeld , Albert . 1966 . The Quintessence of Irving Langmuir Oxford and New York originally published in The Collected Works of Irving Langmuir, eds C. Guy Suits et al., 12 vols (Oxford and New York, 1962), XII, 1–232; Virginia Veeder Westervelt, Incredible Man of Science (Irving Langmuir) (New York, 1968). In 1929 the Dean of Columbia University's Faculty of Applied Science ventured that ‘in the field of scientific accomplishment and its application to the welfare of society Langumir probably stands first’ among all the university's graduates: G. B. Pegram to F. Fackenthal, Secretary, Columbia University, 21 May 1929 (CUA, CF, PF). Four years earlier Columbia had awarded Langmuir an honorary doctorate: Columbia University, Catalogue, 1925–26, 374.
  • Rabi . Molecular Beams 32 – 32 . typescript draft (late 1936, of paper intended for Reviews of Modern Physics), 7 (LC, RP, box 62, fldr 11). For the technique and results of molecular beam research as they stood in 1930, see Ronald G. J. Fraser, Molecular Rays (Cambridge, 1931).
  • Stern, and independently Thomas Johnson (at Yale and following a suggestion of E. O. Lawrence — see note 32), adopted the Pirani-gauge or Hitzdrahtmanometer for detection of beams of molecular hydrogen. Stern ingeniously modified the design to increase its sensitivity by an order of magnitude: Stern, ‘Versuche an Molekularstrahlen’, reported at the Volta centenary congress in Como (note 16), Atti del Congresso … settembre 1927, 117–8, along with his first results indicative of de Broglie wave effects. The contact-ionization detector (which also used a hot wire, but to different effect) was an application of Langmuir and K. H. Kingdon, ‘Thermionic Effects Caused by Alkali Vapors in Vacuum Tubes’, Science 1923 57 58 60 and idem., ‘Thermionic Effects Caused by Vapours of Alkali Metals’, Royal Society of London, Proceedings, A107 (1925), 61–79. Also of great importance for the technique of molecular beams — but not considered in this paper — were Langmuir's contributions to high-vacuum technology. See, for example Theodore E. Madey and William C. Brown, editors, History of Vacuum Science and Technology (New York, 1984), and Paul A. Redhead, editor, Vacuum Science and Technology: Pioneers of the 20th Century (New York, 1994).
  • Langmuir , I. 1917 . ‘The Condensation and Evaporation of Gas Molecules’, National Academy of Sciences of the U.S.A . Proceedings , 3 : 141 – 147 . Gerlach (note 21), ‘Atomstrahlen’ (1924) is devoted chiefly to discussion of the deposits, of which Stern and Estermann made a special investigation, establishing the minimum ‘developable’ deposit as a mere tenth of an atomic layer: I. Estermann and O. Stern, ‘Über die Sichtbarmachung dünner Silberschichten auf Glas’, Zeitschrift für physikalische Chemie, 106 (1923), 399–402; Estermann, ‘Über die Stuktur dünner Silberniederschläge’, ibid., 403–6 (reporting work done in Rostock). In the work of chemist-turned-physicist R. W. Wood (1921–2) lay the origins of the technique employed by Stern, by Thomas H. Johnson, and, eventually, also by Rabi and collaborators, for both the production and the detection of beams of atomic hydrogen.
  • See Figure 5.3 for such a trace photographically recorded by Rabi. One might have expected that microphotometers, such as were employed to measure spectrographs, would have been applied to the evaluation of Stern—Gerlach Striche — and particularly so since P. P. Koch, the Professor of Experimental Physics in Hamburg, in whose Physikalisches Staatsinstitut Stern's laboratory was located, possessed a microphotometer of world-renowned precision. Interestingly, Stern, ‘Bemerkungen über die Auswertung der Aufspaltungsbilder bei der magnetischen Ablenkung von Molekularstrahlen’ Zeitschrift für Physik 1927 41 563 568 (567–8), said in this foundational discussion of the evaluation problem, apropos the issue of increasing the measurement precision, that by photometry of photographs of Aufspaltungsbilder the decisive parameters ‘are surely very exactly determinable’ — i.e. this is something that Stern had not then as yet done, and I have seen no indication in later papers that it was ever done. Fraser (note 27), Mol. Rays (1931), 130, says ‘The limits of visibility s 1, s 2 of the trace on the target are measured, either directly with ocular micrometer, or more accurately by photometry of a photograph of the deflection pattern’, but he cites no literature.
  • Johnson , Thomas H. 1928 . The Production and Measurement of Molecular Beams . Physical Review , 31 : 103 – 114 . idem., ‘Diffraction of Hydrogen Atoms’, Physical Review, 37 (1931), 847–61; and many publications in the Journal of the Franklin Institute.
  • Nierenberg , W.A. 1959 . Molecular and Atomic Beams at Berkeley Edited by: Estermann . 9 – 42 . New York (9–10); Servos (note 12), Physical Chemistry … in America (1990), 240, relying also on Robert W. Seidel, ‘Physics Research in California: The Rise of a Leading Sector in American Physics’, PhD dissertation, University of California, Berkeley, 1970. Some beam work was done at Princeton, partly with a chemical connection, and it was via this route that chemist Edwin McMillan got to Berkeley, there to succumb to the force of E. O. Lawrence: J. David Jackson and W. K. H. Panofsky, ‘Edwin Mattison McMillan’, National Academy of Sciences of the USA, Biographical Memoirs 69 (1996), 215–42.
  • Forman . 1987 . Behind Quantum Electronics: National Security as Basis for Physical Research in the United States, 1940–1960 . Historical Studies in the Physical Sciences , 18 : 149 – 229 . and ‘Into Quantum Electronics: The Maser as “Gadget” of Cold-War America’, in National Military Establishments and the Advancement of Science and Technology: Studies in Twentieth Century History, ‘Boston Studies in the Philosophy of Science, vol. 180’, eds P. Forman and J. M. Sánchez-Ron (Dordrecht, 1996), 261–326. H. A. Zahl, Electrons Away; or, Tales of a Government Scientist (New York, 1968); ‘Frische, Carl A.’, Current Biography Yearbook, 1962 (New York, 1963), 144–5.
  • Rodebush , Worth H. 1931 . Molecular rays . Reviews of Modern Physics , 3 : 392 – 411 . (392). John Servos, who has saved me from mislabelling Wood as physical chemist, points out that rodebush was a student of G. N. Lewis and emphasizes that Lewis had long been of the view that magnetism was the key to atomic and molecular structure. For example, G. N. Lewis, Valence and the Structure of Atoms and Molecules (1923; repr. New York, 1966), 32, 52, et passim.
  • Stern . 1927 . Bemerkungen über die Auswertung der Aufspaltungsbilder bei der magnetischen Ablenkung von Molekularstrahlen . Zeitschrift für Physik , 41 : 563 – 568 . Zeitschrift für Physik, 41 (1927), 567–8, is extremely critical of Taylor's measurements of the magnetic moments of K and Na; Stern (F. Knauer and O. Stern), ‘Intensitätsmessungen an Molekularstrahlen von Gasen’, Zeitschrift für Physik, 53 (1929), 766–78 (767), is moderately critical of Johnson's measurements, and, ‘Über die Reflexion von Molekularstrahlen’, Zeitschrift für Physik, 53 (1929), 779–91 (791), highly critical of Ellett and Olson's.
  • Kunz , Jacob , Taylor , John B. and Rodebush , Worth H. 1926 . The Magnetic Properties of Atoms . Science , 53 : 550 – 551 . Taylor, ‘Magnetic Moments of the Alkali Metal Atoms’, Physical Review, 28 (1926), 576–83; T. E. Phipps and J. B. Taylor, ‘The Magnetic Moment of Atomic Hydrogen’, Science, 54 (1926), 480–1; T. E. Phipps and J. B. Taylor, ‘The Magnetic Moment of the Hydrogen Atom’, Physical Review, 29 (1927), 309–20; Worth H. Rodebush, ‘The Effect of Velocity Distribution on the Deflection of Atoms in an Inhomogeneous Magnetic Field’, National Academy of Sciences of the USA, Proceedings, 13 (1927), 50–2; John B. Taylor and T. E. Phipps, ‘The Magnetic Moment of Atomic Iodine’, Physical Review, 29 (1927), 904, abstract of paper presented at the Am. Phys. Soc. meeting Washington, DC, 22–3 April; O. E. Kurt and T. E. Phipps, ‘The Magnetic Moment of the Oxygen Atom’, Physical Review, 34 (1929), 1357–66; A. N. Guthrie and M. J. Copley, ‘The Magnetic Moment of the Palladium Atom’, Physical Review, 38 (1931), 360–4; M. J. Copley and T. E. Phipps, ‘The Surface Ionization of Potassium on Tungsten’, Physical Review, 48 (1935), 960–8.
  • Gerlach . 1927 . Das magnetische Verhalten von Gasen und Dämpfen . Atti del Congresso Internazionale dei Fisici , Settembre in 11–20 on the first page of his Como Congress paper, pointed to ‘the measurements on atomic beams which have been further advanced in recent years especially by the experiments in the Hamburg physical-chemical institute by O. Stern and his collaborators as well as in America by Taylor’, and, on p. 79, credits ‘the measurements by Stern and Leu, as also those by Taylor’ as demonstrating that alkali atoms have ‘vollkommene Richtungsquantelung’ and one Bohr magneton.
  • Rabi's charge (December 1963). p. 1, of precisionism against Cornell physics — by no means fully justified — perhaps reflects his experience in Physics 14, his second and most advanced physics course, ‘required of candidates for B. Chem., M. E. and E. E. … Physical measurements in properties of matter, mechanics, heat, light, sound, magnetism and electricity; the adjustment and use of instruments of precision. Results and errors are carefully discussed Announcement of the College of Arts and Sciences, 1922–23 Cornell University 52 52 The description of this course, supervised by professor Floyd Richtmyer, echoes Richtmyer's address as AAAS Section B Vice-President, in New Orleans, late in December 1931, ‘The Romance of the Next Decimal Place’: Herbert E. Ives, ‘Floyd K. Richtmyer, 1881–1939’, National Academy of Sciences of the USA, Biographical Memoirs, 22 (1941), 71–81. (Rabi attended the meeting at which this address was delivered and presumably heard it: see section 7.)
  • Rabi . 1963 . December : 5 – 5 . idem (13 October 1975), 54, 56; Rigden (note 5), Rabi (1987), 32–3. In these recollections Rabi sharpened the issue of discrimination against Jews by alleging that he was ‘the top student’ in his Cornell class. His grades, however, were barely good: the record kept by the Cornell registrar shows a low B average. For the importance of anti-Semitism in scientific careers in America between the two world wars, see Kevles (note 2), The Physicists (1978, 1995), 210–16, 278–9, 372, 454–5; J. L. Heilbron and Robert W. Seidel, Lawrence and His Laboratory: A History of the Lawrence Berkeley Laboratory, vol. 1 (Berkeley, 1989), 248–58; David A. Hollinger, Science, Jews, and Secular Culture: Studies in Mid-Twentieth Century American Intellectual History (Princeton, 1996), 7–9; and Andrew S. Winston, ‘“As His Name Indicates”: R. S. Woodworth's letters of reference and employment for Jewish psychologists in the 1930s', Journal of the History of the Behavioral Sciences, 32 (1996), 30–43.
  • Rabi . 1978 . i.e. Kevles (note 2), 214
  • Information supplied by Lopes Ms Annette Office of the Registrar Columbia University 1 1 4, and 31 December 1997. This first, failed, attempt at graduate studies in physics does not appear in Rabi's recollections nor in any curriculum vitae that he prepared, and consequently is also absent from all previous biographical works.
  • Indeed, apart from Trevor's two courses on thermodynamics — Rabi took the second, physics 59, ‘Applications of Thermodynamics in Physics’, in his first term — and one course on physical optics by the scientifically undistinguished Harley E. Howe (he gave brilliant demonstration lectures), Kennard taught all of the nine regular graduate courses. Cornell University, Announcement of the College of Arts and Sciences, 1922–23, 55. Joseph Trevor's courses on thermodynamics were notorious for their difficulty; Servos (note 12), 165. Among Rabi's notebooks (LC, RP, box 76, fldr 4) there is one marked on the front cover ‘59/PHYSICS/Thermodynamics/I. I. Rabi’, where the letters of the word ‘PHYSICS’ are written with wavey lines, as though to indicate shivers of terror. Cattell J.McK. American Men of Science , 4th edn New York 1927 1126 1129 ranked ‘the ten strongest departments in each science together with their relative gain or loss since 1906’ on the basis of the number of distinguished researchers they contained. In physics the top ten were Bureau of Standards, Harvard, General Electric, Chicago, Bell Telephone, Johns Hopkins, Columbia, Caltech, Cornell, Yale, with Harvard having more than twice the score of any other university. See also, Kevles (note 2, 1978), 79–80; Forman et al. (note 10), 63; and G. B. Pegram, questionnaire (5 March 1927), cited in section 6.
  • Rabi . 1963 . December : 6 – 7 . idem (29 March 1984), 13. By the mid-1930s, and emphatically in later decades, Rabi was irrationally partial to Columbia; probably physics was, on the whole, taught relatively well at Cornell.
  • Cornell . The Register, 1923–24 , 209 – 209 . lists both Isidor Isaac Rabi and Gertrude Frances Rabi — his younger sister — among the students registered in the Agriculture School's summer session. Rabi took courses on Rural Education. For Harvard and romance, see Rigden (note 5, 1987), 37.
  • The epithet ‘huge’, and the characterization of the student body as ‘immense’ — the enrolment in Columbia's graduate schools was by far the largest in the country, and growing rapidly — is due to its President, Nicholas Murray Butler, in the 18th year of his reign: Columbia University, Annual Report … 1920 1 2 In 1906 Columbia, with 60 of Cattell's ‘thousand leading scientific men’, stood just below Harvard, with 66.5, but in Cattell's 1927 ratings cited above (note 43), Harvard had climbed to 89.5, Columbia had fallen to 46.5, surpassed by Chicago, with 53.5. Columbia's Physics Department had declined far more steeply than any other listed.
  • Not to mention the quite out of date celestial mechanician C. L. Poor, electromechanician M. I. Pupin, and geometrical optician J. P. C. Southall. On Wills, who had been for 20 years chiefly responsible for graduate instruction: Wills, Albert Potter National Cyclopedia of American Biography 1939 27 430 431 and the Webb autobiographical memoir cited below. On Pegram: ‘Pegram, George Braxton’, in National Cyclopedia of American Biography, vol. F (1942), 391–2; vol. 49 (1966), 132–3; L. A. Embrey, ‘George Braxton Pegram’, National Academy of Sciences of the USA, Biographical Memoirs, 41 (1970), 357–407. For Webb, see Manuscript autobiography, ca 1962, 13pp., and interview, 24 April 1970, by Charles Weiner, transcript, 30pp. (AIP, NBL).
  • Pegram's efforts to get modern physics in Columbia's Summer Session, 1915–22, are chronicled by him in notes, 5pp., made in the early 1950s, in CU, PP, box 37, fldr: Summer Session. Sopka Katherine R. Quantum Physics in America, 1920–1935 New York 1980 chapter 2, 42–3, gives a listing of ‘Courses relating to quantum physics at certain American universities ca. 1923–1925’, namely, Berkeley, Caltech, Chicago, Cornell, Harvard, MIT, Michigan, Minnesota, Princeton, Stanford, and Yale, and pertinently noted that ‘the absence of some institutions such as Columbia University and the Johns Hopkins University is noteworthy. Both of these institutions had faculty members capable of giving theoretical courses of a classical nature’ — for Columbia she cites Pegram, Pupin, and Wills — ‘but turned to outside help to cope with quantum physics’. Guest professors in Columbia's Summer Session (early July to mid-August, from Columbia University, Summer Session Announcement, 1921 … 1926, completing and correcting Sopka's listing): 1921, Leigh Page, ‘Radiation and Atomic Structure’ and ‘Principle of Relativity’; 1922, A. W. Hull, ‘X-rays’ and ‘Electron Tubes’; 1923, P. D. Foote, ‘Spectroscopy and Radiation’ and ‘Atomic Structure in Modern Physics’; 1924, A. L. Hughes, ‘Phenomena Relating to Ions, Electrons, and Radiation’ and ‘The Bohr Theory’; 1925, G. N. Lewis, ‘Molecular and Atomic Theory’ and ‘Thermodynamics’; 1926, Leigh Page, ‘Quantum Theory’.
  • On the solicitation of Einstein, see Pegram to Pres. N. M. Butle CUA, CF, PF 1923 May 10
  • Rabi . 1983–85 . 233 – 234 . Pegram . a southerner by birth and breeding, was a man of unusually liberal and democratic sympathies. Perhaps the best that can be said of Columbia in these years is that it placed so much trust and confidence in such a person.
  • Rabi . 1963 . December : 9 – 9 . Rabi (19 October 1975), 56. The moderately luxurious appointments of Hartley Hall, in which Rabi lived, are described in Columbia University, Catalogue, 1929–30, 130–1.
  • Sopka's 1976 dissertation, Quantum Physics in America, 1920–1935 (note 51), is the work that comes closest to exploring this crucial transformation in the culture of American physics (especially chapters 1, 67–9; 2, 44, 51–3; 3, 69–71), yet she never deals directly with the question of ‘principled’ objections to purely theoretical dissertations or confronts the question what, exactly, ‘the change in the American attitude toward theoretical activity in physics that came about during the 1920s’ was. Weart Spencer The Physics Business in America, 1919–1940: A Statistical Reconnaissance The Sciences in the American Context Reingold Nathan Washington 1979 295 358 (300–1), offers some insightful observations regarding this transformation.
  • The dissertation: Kronig R.deL. Change of Conductance of Selenium Due to Electronic Bombardment Physical Review 1924 24 377 382 submitted 26 May 1924. The calculations: Kronig to Kramers, 28 April 1924 (SHQP microfilm 8). The measurements: A. P. Wills and L. G. Hector, ‘The Magnetic Susceptibility of Oxygen, Hydrogen and Helium’, Physical Review, 23 (1924), 209–20. The first (and for a long time after the only) theoretical dissertation done at Columbia was that of Shou Chin Wang, completed in the spring of 1928, nominally under Wills' supervision: S. C. Wang, ‘The Normal Hydrogen Molecule’, Physical Review, 31 (1928), 579–86. Sopka (note 51), Quantum Physics in America (1980), chapter 3, 102, reports ‘with regard to the circumstances under which Wang wrote his thesis, he has told me (telephone conversation 20 May 1974) that he had departmental approval of and satisfaction with his work, although Columbia's professor of mathematical physics at that time, A. P. Wills, was a theoretician of the old school’. It should be noted, however, that Wang could presumably establish possession of the indispensable experience of experimental research, having an M. S. from Cornell, an M. A. from Harvard, and being engaged as a research assistant to Columbia experimental physicist Harold W. Webb.
  • Rabi . 1927 . On the Principal Magnetic Susceptibilities of Crystals . Physical Review , 29 : 174 – 185 . Wills had proposed measurement of the susceptibility of sodium vapour to Rabi as dissertation topic, but in view of the difficulty of this experiment — the measurement of the susceptibility of an alkali vapour was first achieved by Gerlach (note 16), Como, 1927, and his student A. Roth — Rabi refused it and found his own ‘magnetic’ topic. Rabi's notebook marked ‘Research’ (LC, RP, box 75, fldr 1) relates to his dissertation and has dated entries from December 1924 to April 1926.
  • Rabi . 1927 . On the Principal Magnetic Susceptibilities of Crystals . Phys. Rev. , 29 : 174 – 174 . Weiss (note 17), Phys. Zeitschr., 12 (1911), 944–7, in arguing for his magneton, had drawn support from measurements of susceptibility that Wills had made as an advanced student in Germany circa 1900. And the method that Rabi devised was an adaptation to small crystals of a technique that Wills had there used — Wills had it from his mentor there, Henri du Bois — and had continued to use, and that he had recently adapted to the measurement of the susceptibility of gases: Wills and Hector (note 58), Phys. Rev., 23 (1924). The experimental determination of the Weiss magneton numbers for each of the principal crystallographic axes of each of the Tutton salts was part of Rabi's program, with the Bohr magneton numbers computed from these. Rabi, like Wills, made reference to Pauli's publications and interpretations, but he made no commitment, and rather seems to have regarded the Weiss magnetons as realer.
  • Rabi . 1975 . October : 70 – 70 . 13
  • Condon to Rabi, December 1927 7 (LC, RP, box 2, fldr 5)
  • Bitter , Francis . 1929 . Diamagnetismus und Wellenmechanik . Physikalische Zeitschrift , 30 : 497 – 504 . Bitter, ‘On the Diamagnetism of Electrons in Metals’, National Academy of Sciences of the USA, Proceedings, 16 (1930), 95–8; Bitter, Magnets: The Education of a Physicist (New York, 1959); Thomas Erber, ‘Francis Bitter: A Biographical Sketch’, in Francis Bitter: Selected Papers and Commentaries, eds T. Erber and C. M. Fowler (Cambridge, Mass., 1969), 3–19 (7–8), and Bitter's first papers, being measurements of magnetic susceptibilities of gases, reprinted ibid., 31–64. Lillian Hoddeson, Gordon Baym, and Michael Eckert, ‘The Development of the Quantum Mechanical Electron Theory of Metals, 1926–1933’, in Out of the Crystal Maze: Chapters from the History of Solid-State Physics, ed. Lillian Hoddeson et al. (Oxford, 1992), 88–181 (125).
  • Bitter . 1929 . Diamagnetismus und Wellenmechanik . Physikalische Zeitschrift , 30 : 497 – 504 . Magnets (1959), 72–6.
  • Rabi . 1962–3 . : 28 – 28 . Rabi (1 December 1963), 10; Rabi (13 October 1975), 78; Rabi (note 8), ‘Stern (obit.)’, (1969), 104; Rabi (1978); Rabi (1988), 119.
  • Rabi, notebook marked ‘Research’ (LC, RP, box 75, fldr 1). Rabi (1962–3), 69. Rigden's scholarly study of ‘Molecular Beam Experiments on the Hydrogens during the 1930s’ Rabi 1987 40 45 Presumably Rabi was under pressure to finish up his experimental work by July 1926, when the Physics Department relocated from Fayerweather Hall to the new Physics Laboratories (subsequently, Pupin).
  • The laboratory and its facilities is described in a 26-page brochure privately printed by Columbia The New Physics Laboratories of Columbia University in the City of New York, 1927 New York 1927 Occupation date: Columbia Univ., Catalogue, 1926–27, 231. (Further description given in section 6.)
  • In an undated letter to Wm. Tisdale, Rabi (c.4 February 1928), supplementing his application for an International Education Board Fellowship, stated that ‘During the scholastic year 1926–27 … I carried on some further measurements of crystal susceptibilities which are as yet unfinished due to the interruption of my European trip’. (Rabi folder, nr. 937, in IEB records, Rockefeller Archives Center, RG 29, series 1, subseries 3). Among the ‘apparatus for research’ acquired for the new laboratories was a ‘Magnet by F. Pearson, $1350.00’ (Pegram to N. M. Butler, 9 December 1927, CUA, CF, PF). This ‘large electric magnet which we bought recently’ was subsequently described by Pegram to W. W. Stifler, Amherst College, 14 March 1928 (CU, PP, box 9, fldr: S-Misc): ‘The magnet is built by the mechanician of the Department of Physics of the Univ. of Chicago, Mr. F. Pearson. It costs $1800 (sic). It weighs 800 lbs, is water cooled, takes a maximum current of 10 amperes, and is designed to give a field of 35,000 gausses with 10 mm pole pieces, 4 mm apart’. This, presumably, is the magnet that figured in Bitter's recollection of his search for a dissertation topic, probably in the summer or fall of 1927: ‘walking rather disconsolately around the corridors wondering … my eye lit on an impressive looking magnet in an empty laboratory’. Bitter (note 64), Magnets (1959), 17, confirmed on 66, where Bitter describes going ‘up to the eighth floor of the Columbia Physics Building’ to see Wills about selecting a thesis topic. It seems probable that the magnet was of a Weiss design, i.e. the now standard design of massive squared ‘U’ yoke with cylindrical poles, approaching each other through holes in the upper ends of the legs of the ‘U’, and surrounded by large, vertical ‘pancake’ coils inside the yoke. (The poles would have been about 10 cm in diameter, tapered pole pieces bringing them down to the 10 mm cited by Pegram.) A Weiss-type electromagnet, presumably smaller than that purchased in 1927, was used by Rabi for his dissertation research (no details given beyond the designation ‘Weiss’). The original description: Weiss Pierre Electro-aimant de grande puissance Bulletin des séances de la Société Française de Physique 1907 124 140
  • Kronig , R.deL. 1960 . “ The Turning Point ” . In Theoretical Physics in the Twentieth Century: A Memorial Volume to Wolfgang Pauli Edited by: Fierz , M. and Weisskopf , V.F. 5 – 39 . New York Kronig to Bohr, 21 December 1925 (AHQP, Bohr Scientific Corresp., microfilm 13). Kronig's appointment was as Lecturer, i.e. sub-professorial, both in 1925–6, and in 1926–7, at a mere $2000 for the 1926–7 academic year. In the spring of 1927, as Kronig's fame was spreading, Pegram, anxious that Columbia not lose him, wrote President Butler, 19 May 1927 (CU, PP, box 2, fldr ‘Nicholas Murray Butler’) proposing to advance him to Assistant Professor at $3000. Although Pegram could then say that ‘Kronig seems to be very content here’, in fact, Kronig, who had had all of his secondary education in Europe, disdained American culture generally and American physics particularly: Kronig to Kramers, 7 February 1926 (SHQP microfilm 28), 6 March 1926 and 17 September (SHQP microfilm 10); Kronig to Bohr, 7 October 1926 (AHQP, Bohr Scientific Corresp. microfilm 13). Indeed, in the above cited memoir, Kronig never mentioned Columbia, either as an institution at which he studied or as one at which he taught.
  • A subset of this seminar, namely Columbia students studying wave mechanics under Kronig's guidance, appear in a group photograph, reproduced in Rigden Molecular Beam Experiments on the Hydrogens during the 1930s Historical Studies in the Physical Sciences 1983 335 373 13 Rabi (1987), following p. 112, with Schrödinger's equation prominent on the blackboard behind them, and a Heft of the Annalen der Physik (the journal in which Schrödinger's papers appeared) in Kronig's hand. Presumably Rabi, with his penchant for signature self-portraiture — cf. Figure 5.2 — was the director and photographer as well as one of the subjects.
  • Rabi . 1963 . December : 10 – 11 . 16; Rabi (29 March 1984), 14. Kronig, interview for SHQP, 12 November 1962, by J. L. Heilbron, transcript 25pp. in AHQP (pp. 20–1). Kronig to K. R. Sopka, 18 June 1974, quoted at length by Sopka (note 51), Quantum Physics in America (1980), chapter 3, 49–50, 97, who also references information given her by S. C. Wang in telephone conversations. In 1929 the senior NYU participant, F. Wheeler Loomis, became head of the Physics Department at the University of Illinois, from where his friendship and high regard for Rabi would have important consequences for Rabi's career.
  • Rabi . 1984 . March : 14 – 14 . 29 ‘we had a group of graduate students who were wonderful people. A chap by the name of Wong, an absolute whiz’. Wang — pronounced ‘Wong’ — impressed Kramers very favourably with his intelligence and cleverness when they worked together in the summer of 1928: ‘he will certainly develop into a very good physicist’. Kramers to Pegram, 15 July 1928 (CU, PP, box 5, fldr: K-Misc). Wang taught the company to eat with chop sticks and ensured that they got authentic dishes when, customarily, after the seminar they went to dinner together at a Chinese restaurant.
  • Kronig , R.deL. and Rabi , I.I. 1926 . The Symmetrical Top in the Undulatory Mechanics . Nature , 118 : 805 – 805 . and Kronig and Rabi, ‘The Symmetrical Top in the Undulatory Mechanics’, Physical Review, 29 (1927), 262–9.
  • Kronig to Kramers (SHQP microfilm 10), proposing experiments with alpha particles in magnetic fields (absorption and emission) 1926 March 6 and 17 September
  • Kronig . 1926 . Spinning electrons and the Structure of Spectra . Nature , 117 : 550 – 550 . Rabi, ‘Spinning Electrons’, Nature, 118 (1926), 228. Kronig, ‘The Dielectric Constant of Diatomic Dipole-Gases on the New Quantum Mechanics’, National Academy of Sciences of the USA, Proceedings, 12 (1926), 488–93, for which Kronig credits Rabi's stimulus in his letter-memoir quoted by Sopka (note 51), chapter 3, 49–50, 97.
  • Kronig to Bohr AHQP, Bohr Scientific Corresp. microfilm 13 1927 February 7
  • Kronig to Kramers SHQP microfilm 10 1926 September 7 ‘Wenn Atomkerne ein magnetisches Moment und infolgedessen Richtungsquantelung im Feld aufweisen, und ferner beim radioaktiven Zerfall die α-Teilchen unter einem bestimmten Winkel gegen die Kernachse (z.B. entlang der Achse) ausgesandt werden, sollte man erwarten, dass bei Anwesenheit eines Magnetfeldes eine Häufung der α-Teilchen in gewissen Richtungen eintritt’. Kronig (note 77), Nature, 117 (1926), 550.
  • For Rabi's ‘Barnard Fellowship’ and the fiction of remote guidance: Columbia Univ. Catalogue 1925–26 403 403 Pegram to F. D. Fackenthal, 20 May 1927 (CUA, CF, PF); LC, RP, box 18, fldr 6; box 20, fldr 13. The remote guidance was not a total fiction: our knowledge of Rabi's two years in Europe depends largely on letters that he wrote to Pegram partly in fulfilment of this nominal obligation to receive advice and consent. The principal source of funds for Columbia's travelling fellowships was the donation of Mrs W. Bayard Cutting — Kronig had held one of these exceptionally well- paying fellowships — which however was restricted by an ‘anti-immigrant’ provision: Columbia University, Catalogue, 1926–1927, 420; Pegram to Butler, 30 April 1938; Pegram to Mrs Cutting, 4 May 1938; Pegram to Butler, 12 May 1938 (CUA, CF, PF).
  • Rabi . 1962–3 . : 70 – 76 . Rabi (1983–5), 302–4. Rabi to Pegram, 1 September 1927 (CU, PP, box 8, fldr ‘R-misc’), previously summarized by Kevles: Rabi (1978). Rabi, unidentified ms sheet (draft of application for a Guggenheim fellowship, early November 1927) (LC, RP, box 95, fldr 10).
  • Rabi . c.4pp. of MS draft for a paper ‘Diamagnetic Susceptibility and Dielectric Constant of the Hydrogen Molecule on the New Quantum Mechanics’, intended for the National Academy of Sciences of the USA, Proceedings (LC, RP, box 76, fldr 6). Rabi (1962–3), 76–80; Rabi (13 October 1975), 70. Rigden (note 5), 57–8. Wills to Rabi, 9 September 1927 (LC, RP, box 9, fldr 2). Rabi, c.8pp. of MS draft for a paper on the Glaser effect (autumn 1927) (LC, RP, box 76, fldr 6).
  • Glaser , A. 1925 . Über eine neue Erscheinung am Diamagnetismus der Gase . Physikalische Zeitschrift , 22 : 212 – 217 . (Glaser's presentation at the Innsbruck Naturforscherversammlung, with critical discussion by Sommerfeld, Einstein, and, especially, Pauli). A fuller presentation, with effusive acknowledgement of Wien's aid and guidance, was published under the same title in Annalen der Physik, 75 (1924), 459–88. In this latter journal, edited by Wien, Glaser continued in the following years to publish confirmations of his ‘Anomalie’. ‘In view of the magnetic work done there’, Rabi wrote Pegram, 1 September 1927 (CU, PP, box 8, fldr: R-Misc.), ‘I was particularly interested in going through Wien's experimental institute’.
  • Van Vleck . 1932 . “ The Theory of Electric and Magnetic Susceptibilities ” . In Susceptibilities 110 – 113 . Oxford 1932 Gerlach came out quickly as a sceptical critic of Glaser's work: Gerlach (note 62) Phys. Zeits., 26 (1925), 822–3, and Gerlach (note 16), Como, 1927. It was, however, Bitter who, in 1930, showed definitely that Glaser's anomaly was an artifact, due to water vapour: Edmund C. Stoner, Magnetism and Matter (London, 1934), 274–5, 279.
  • Nishina , Y. 1928 . Der wahre Absorptionskoeffizient der Röntgenstrahlen nach der Quantentheorie (nach einer gemeinsam mit I. I. Rabi ausgeführten Arbeit) . Verhandlungen der Deutschen Physikalischen Gesellschaft , 9 : 6 – 9 . presented at the meeting of the Gauverein Niedersachsen in Göttingen, 4–5 February 1928. J. A. Stratton to Rabi, 24 August 1927 (LC, RP, box 8, fldr 3). Kronig's work on X-ray dispersion and absorption, discussed in the ‘Sunday seminar’ (Kronig to Sopka, 18 June 1974), was prompted in part by the experimental demonstration of refraction of X-rays by a crystal prism by Bergen Davis, Columbia's most prolific and most highly regarded experimentalist: B. Davis and C. M. Slack, ‘Measurement of the Refraction of X-rays in a Prism by Means of the Double X-ray Spectrometer’, Physical Review, 27 (1926), 18–22; Kronig to Kramers, 11 March 1926 (SHQP microfilm 10), referring also to Kronig's correspondence with Richtmyer. Regarding Richtmyer see (note 39).
  • Svein Rosseland to Rabi December 1927 28 (LC, RP, box 7, fldr 6) gives a graphic description of Bohr's literary travail. Rabi (1962–3), 77–9, acknowledging that Nishina ‘had been at Copenhagen for a number of years and was a great favorite’, states that ‘there was nothing personal’ about his being sent by Bohr to Pauli.
  • Pauli , Wolfgang . 1927 . Über Gasentartung und Paramagnetismus . Zeitschrift für Physik , 41 : 81 – 102 . Pauli, ‘Die Quantenmechanik des magnetischen Elektrons’, Zeitschrift für Physik, 43 (1927), 601–23. Hoddeson, Baym, Eckert (note 64), ‘Quantum Mechanical Electron Theory of Metals’ (1992), 93–7.
  • 1927 . Vorlesungsverzeichnis . Physikalische Zeitschrift , 28 : 742 – 742 . published Rabi, sheet of notes, ‘Pauli Nov. 3, 1927 Erste Vorlesung. Quantenmechanik' (LC, RP, box 72, fldr 9). Rabi to Richtmyer, 22 January 1929 (LC, RP, box 7 fldr 7): ‘In addition to my own knowledge I have notes of a course of Pauli and Gordon that I attended where the subject is developed with great elegance and simplicity’. (Walter Gordon was theoretical assistant in the Hamburg Institute for Experimental Physics.)
  • Rabi to Pegram December 1927 14 (CU, PP, box 8, fldr: R-Misc). Only Kevles — Rabi (1978) — has drawn on this important source for Rabi's European period.
  • On Dirac's electron theory, see Kragh Helge Dirac: A Scientific Biography Cambridge 1990 and S. S. Schweber, QED and the Men Who Made It (Princeton, 1994), chapter 1. Rabi, ‘Das freie Elektron im homogenen Magnetfeld nach der Diracschen Theorie’, Zeitschrift für Physik, 49 (1928), 507–11; Darwin to Rabi, 11 April 1928 (LC, RP, box 2, fldr 12). The question of Rabi's interests, conceptions and intentions in this general direction — electronic orbits and energy levels in magnetic fields — remains to be explored. It reconnects with his work as a molecular beamist through the much mooted question of the measurability of the magnetic moment of the free electron by means of a Stern-Gerlach experiment, on which see Olivier Darrigol, ‘A History of the Question: Can Free Electrons Be Polarized?’, Historical Studies in the Physical Sciences, 15 (1984), 39–79. To this question I hope to return in a future publication.
  • Rabi . Molecular beams 32 – 32 . ‘Molecular Beams’, draft, 7.
  • Stern . 1921 . Ein Weg zur experimentellen Prüfung der Richtungsquantelung im Magnetfeld . Zeitschrift für Physik , 7 : 249 – 253 . ZsP, 7 (1921), 253; Stern (note 9), 1961 interview, 25. Henri du Bois, ‘Neue Halbring-Elektromagnete’, Zeitschrift für Instrumentenkunde, 31 (1911), 362–78, with a magnetic field approaching 30 kilogauss, boasted of the gradients of 2 × 104 gauss/cm that he obtained with canted conical pole pieces.
  • Gerlach and Stern . 1921 . Der experimentelle Nachweis des magnetischen Moments des Silberatoms . Zeitschrift für Physik , 8 : 110 – 111 . ZsP, 8 (1921), using beams with circular cross-section obtained a broadening corresponding to μ = 1–2μB; Gerlach and Stern (note 21), Ann. d. Phys., 74 (1924), 675, 689.
  • The method is described by Gerlach Stern Ann. d. Phys. 1924 74 691 693 where, however the susceptibility χ, though referred to, does not appear in the symbolic expressions. This is remedied in U.z.M. Nr. 4: Alfred Leu, ‘Versuche über die Ablenkung von Molekularstrahlen im Magnetfeld’, Zeitschrift für Physik, 41 (1927), 551–62 (556–8), Leu's Hamburg dissertation. Stern (note 30), U.z.M. Nr. 5, recognized that χ is a weak point of the method; but also bismuth's magnetoresistance was not without its uncertainties: P. Kapitza, ‘The Study of the Specific Resistance of Bismuth Crystals and Its Change in Strong Magnetic Fields and Some Allied Problems’, Proceedings of the Royal Society of London, A119 (1928), 358–386.
  • Gerlach and Stern . 1921 . Der experimentelle Nachweis des magnetischen Moments des Silberatoms . Zeitschrift für Physik , 8 : 110 – 111 . ZsP, 9 (1922), 353–55. The accuracy claimed was sufficient to exclude the Weiss magneton. Gerlach (note 21), Ann. d. Physik, 76 (1925).
  • Segrè . 1973 . National Academy of Sciences of the USA . Biographical Memoirs , 43 : 214 – 236 . ‘Stern’, N. A. S., Biogr. Mem. (1973). Emilio Segrè, A Mind Always in Motion: The Autobiography of Emilio Segrè (Berkeley, 1993), 70.
  • Stern . 1926 . Zur Methode der Molekularstrahlen (Untersuchungen zur Molekularstrahlmethode, Nr. 1) . Zeitschrift für Physik , 39 : 751 – 763 . U.z.M. Nr. 1 (pp. 754–6).
  • Stern , O. and Volmer , M. 1919 . Sind die Abweichungen der Atomgewichte von der Ganzzahligkeit durch Isotopie erklärbar? . Annalen der Physik , 59 : 225 – 238 . W. Lenz, ‘Über ein invertiertes Bohrsches Model’, Bayerische Akademie der Wissenschaften, München, Sitzungsberichte der mathematischphysikalischen Klasse (1918), 355–65.
  • Stern . 1926 . Zur Methode der Molekularstrahlen (Untersuchungen zur Molekularstrahlmethode, Nr. 1) . Zeitschrift für Physik , 39 : 751 – 763 . Zs. f. Phys. 39 (1926), 759–60. To appreciate just how daunting such an undertaking then appeared — still appeared 5 years later to a capable molecular beamist who had spent 2 years in Stern's laboratory — it is necessary only to read Fraser's discussion in Molecular Rays (note 27) 147–9: ‘The difficulties of spectroscopic observation are, however, so great that up to the present it has not been found possible to do more than demonstrate the existence of nuclear moments of the expected order of magnitude, 10−3μB. It is therefore important to see how far the molecular ray method is capable of being developed to measure moments of this order; it being remembered at the outset that the method is restricted in any event, with the resolution so far obtained, to atoms or molecules (such as Zn, Cd, Hg, etc.; H2O, H2, etc.) which do not possess an electronic magnetic moment. In the first place, it is clear that inhomogeneities far in excess of the 104 gauss/cm. sufficient for the determination of electronic moments are necessary … at least 106 gauss/cm. Such a high inhomogeneity can however be maintained in a region whose cross section is at the most 0·1 × 0·1 mm, which immediately sets a limit h ∼ 0·1 mm. to the slit length … the intensity is thereby so drastically diminished as to be experimentally useless’.
  • Knauer , F. and Stern , O. 1926 . Der Nachweis kleiner magnetischer Momente von Molekülen . Zeitschrift für Physik , 39 : 780 – 786 . (U.z.M. Nr. 3)
  • Pauli . 1924 . Zur Frage der theoretischen Deutung der Satelliten einiger Spektrallinien und ihrer Beeinflussung durch magnetische Felder . Naturwissenschaften , 12 : 741 – 743 . Pauli devoted the last paragraph of his treatise on the old quantum theory, completed late in 1925, to restating and strengthening his argument that the hyperfine structures point to ‘the presence of a non-vanishing net angular momentum of the nucleus’ — again, without reference to Stern: Pauli, ‘Quantentheoire’, in Handbuch der Physik, eds H. Geiger and K. Scheel, vol. 23 (Berlin, 1926), 1–278 (277). Stern's point is that the effects of such small magnetic moments must lie beyond the sensitivity of optical methods, i.e. he is evidently genuinely unaware of the spectroscopic work invoked by Pauli. In later years Pauli would make a point of his priority — and of the neglect of his proposal when made.
  • Kronig . 1926 . Spinning electrons and the Structure of Spectra . Nature , 117 : 550 – 550 . Roger H. Stuewer, ‘The Nuclear Electron Hypothesis’, in Otto Hahn and the Rise of Nuclear Physics, ed. William R. Shea (Dordrecht, 1983), 19–67.
  • Heisenberg , W. 1926 . Über die Spektra von Atomsystemen mit zwei Elektronen . Zeitschrift für Physik , 39 : 499 – 518 . received 24 July 1926. Linus Pauling and Samuel Goudsmit, The Structure of Line Spectra (New York, 1930), preface dated February 1930, refer to Heisenberg's surmise in two places, pp. 224, 229, and consider it still a possibility, Taylor's test (cit. infra) notwithstanding. But already in January 1930 Goudsmit and his student Lloyd Young, ‘The Nuclear Moment of Lithium’, Nature, 125 (1930), 461–2, had, from analysis of the spectroscopic data, come to the conclusion that ‘the nuclear magnetic moment is not very large, and that the wide hyperfine structure is caused by the presence of a single ls electron in the configurations considered’. Nonetheless, as late as 1932, a big magnetic moment could still be put forward as a real possibility: W. Meissner and H. Scheffers, ‘Präzisionsbestimmung der magnetischen Momente von Kalium und Lithium in Hinblick auf ihr magnetisches Kernmoment, I’, Physikalische Zeitschrift, 34 (1 January 1933), 48–53, although this was probably rhetorical motivation of their experiment. Opening a discussion unnoticed by the editors of his collected papers, E. Fermi, ‘Sur les moments magnétiques des noyaux’, conseil de physique (Solvay) … 1930 (note 62; cf. note 111), 65–80, explained that ‘It is generally admitted that the nucleus of an atom of atomic mass M and atomic number Z is composed of Np = M protons, and Ne = M-Z electrons. In the following we will base ourselves always on this hypothesis’. And he then continued: ‘The first question presenting itself is how is it possible that this moment (i.e. the nuclear magnetic moment) is so weak although the nucleus contains electrons.’ In answer to his rhetorical question, Fermi pointed immediately to Gregory Breit's observation that the magnetic moment of a Dirac electron ‘très étroitement lié’ appears from its exterior effects to be very weak. (Of Breit's efforts in this arena more will be said below.) Fermi's discussion and Briet's contribution, and, more important, Heisenberg's hypothesis and the discussions and investigations that followed therefrom, are all overlooked by Stuewer (note 104).
  • Taylor , John B. 1928 . Das magnetische Moment des Lithiumatoms . Zeitschrift für Physik , 52 : 846 – 852 .
  • Rabi . 1963 . December : 26 – 26 . was quite definite that the development of the contact-ionization method was ‘at Langmuir's suggestion’ (cf. caption to Figure 2.3). Rabi, in his various recollections, repeatedly emphasized Taylor's talents as experimentalist: ‘John Taylor was a most gifted experimenter … His eye was not just focused on his own result, but he was alert to everything that happened’ ([1962–3], 96); ‘John Taylor, a marvelous experimenter’ ([29 March 1984], 15). Among Taylor's contributions was the reintroduction of the metal vacuum chamber, what Stern and Gerlach had used in Frankfurt but Stern had rejected in Hamburg in favour of glass.
  • Taylor . 1929 . Eine Method zur direkten Messung der Intensitätsverteilung in Molekularstrahlen . Zeitschrift für Physik , 57 : 242 – 248 . In a 15 February 1928 report to the International Education Board on his fellowship activities (note 106), Taylor stated that the lithium experiment would be repeated only ‘should the unusual multiple deflection appear’, and in that case ‘For accurate measurement it is proposed to use some form of electron or positive ion pressure gage placed in the path of the ray’.
  • Taylor . 1930 . The Reflection of Beams of the Alkali Metals from Crystals . Physical Review , 35 : 375 – 380 . Stern too was to have gone to Berkeley at the end of December 1928 to lecture during the Winter Quarter, but cancelled the trip because these experiments were finally working well. From Berkeley, Taylor would go to work for Langmuir at the General Electric Research Laboratory in Schenectady, at a 9-to-5 pace, on problems much more directly related to products. In January 1937 he died of septicaemia from a ruptured appendix: Gladys (Mrs John) Taylor to Rabi, 22 January 1937 (LC, RP, box 8, fldr 6); Schenectady Gazette, 23 January 1937.
  • Goudsmit and Young . 1930 . The Nuclear Moment of Lithium . Nature , 125 : 461 – 461 . E. Fermi, ‘Magnetic Moments of Atomic Nuclei’, Nature, 125 (1930), 16, dated 4 December 1929; Fermi, ‘Über die magnetischen Momente der Atomkerne’, Zeitschrift für Physik, 60 (1930), 320–33; Fermi, Collected Papers (Chicago and Rome, 1962), I, 328–9, 336–48. In his presentation to the sixth Solvay Congress in October 1930, Fermi (note 105) explained with characteristic caution that ‘The magnetic moment of an electron, equal to the Bohr magneton, is given by μo = eh4πm o c. It is natural to accept, although one has no experimental proof of it, that an analogous expression holds for the proton. Under this hypothesis, the magnetic moment of the proton would be μp = eh/4πm p c, where m p is the mass of the proton. … This hypothesis, which rests on the idea of a close analogy between the proton and the electron, gains some verisimilitude from the fact that the angular momentum of the proton has the same value h/4π as for the electron’ (p. 68, my translation). And in a paper submitted at this same time, the usually very cautious Breit simply took it for granted that μp = μB40: G. Breit and F. W. Doermann, ‘The Magnetic Moment of the Li7 Nucleus’ Physical Review, 36 (1930), 1262–4. As late as February 1933, when Stern's results were already rumoured, Goudsmit's soon to be much-relied-on paper, ‘Nuclear Magnetic Moments’, Physical Review, 43 (1933), 636–9, containing ‘approximate formulas … for the calculation of nuclear magnetic moments from observed hyperfine structure separations’, expressed those nuclear magnetic moments ‘in “proton magnetons” eh/4πMc, M being the mass of the proton’
  • Quoting the brief announcement for the Anglo-Saxon world to which all three were emigrating Estermann I. Frisch R. Stern O. Magnetic Moment of the Proton Nature 1933 132 169 170 dated 19 June. Their estimated accuracy: 10%. (There is, by the way, a factor of 2 missing from the denominator of their expressions in this paper for the magnetic moment of the electron and the expected magnetic moment of the proton.) Stern's detailed results were submitted for separate publication in May and July: R. Frisch and O. Stern, ‘Über die magnetische Ablenkung von Wasserstoffmolekülen und das magnetische Moment des Protons. I’, Zeitschrift für Physik, 85 (1933), 4–16; I. Estermann and O. Stern, ‘Über die … des Protons. II’, Zeitschrift für Physik, 85 (1933), 17–24. Further, G. C. Wick, ‘Über das magnetische Moment eines rotierenden Wasserstoffmoleküls’, Zeitschrift für Physik, 85 (1933), 25–28. Detailed discussion in Estermann (note 8), American Journal of Physics, 43 (1975), 661–71, and in Rigden (note 5) HSPS, 13 (1983), 339–44.
  • A typical statement, here quoted from Walter W. Otto Stern: Leistung und Schicksal Hochschulalltag im ‘Dritten Reich’: Die Hamburger Universität 1933–1945 et al. Berlin and Hamburg 1991 1143 1143 in
  • For example Fermi Sur les moments magnétiques des noyaux conseil de physique (Solvay) … 1930 65 80 (note 62; cf. note 111) in his report on nuclear magnetism at the October 1930 Solvay Congress, simply denied the possibility of measuring by means of a Stern-Gerlach experiment a magnetic moment so small as a thousandth of a Bohr magneton. In the following discussion, Stern (p. 75) gently took issue, referring to his experiments on mercury and water vapour. On conventional accounts and hortatory messages: P. Forman, ‘The Discovery of the Diffraction of X-rays by Crystals: A Critique of the Myths’, Archive for History of Exact Sciences, 6 (1969), 38–71.
  • This term is taken from a letter by Victor W. Cohen to Rabi October 1934 6 (LC, RP, box 2, fldr 9), written a month or two after Cohen, PhD in hand, had left Rabi's laboratory and New York City for a postdoctoral position with Alexander Ellett in Iowa City. Cohen uses the term, with light irony, evidently, in sending his greetings to the group of researchers around Rabi, implying, it would seem, a self-conception in that group of reproducing something of Stern's Hamburg laboratory — its supposed sociality as well as its scientific orientation.
  • Rabi . 1963 . December : 21 – 21 . Rigden (note 5), Rabi (1987), 60. It should be said that Fraser, as his papers (see note 119) and his correspondence with Rabi (LC, RP, box 3, fldr 10) show, had quite adequate theoretical ability (and not impressed by Langmuir's pretence to such).
  • December 1927 . Rabi to Pegram December , 14 (CU, PP, box 8, fldr: R-Misc), observing that ‘the experimental methods have been refined far beyond the old work of Stern and Gerlach’.
  • As Stern remarked at this time in recommending one of his students, a ‘Physiko-Chemiker’, to Lise Meitner as an assistant: ‘He's very capable; a born chemist.’ (‘Er ist recht ordentlich, von Natur aus Chemiker’.) Stern to Meitner Meitner Papers, Churchill College Archives Cambridge University 1928 March 30
  • Fraser, on the other hand, was a physicist who, through molecular beams, became a physical chemist. A Scot, born in 1899, Fraser studied at Aberdeen (BSc 1924, PhD 1926) working closely with Thomson G.P. Three publications resulted: Fraser, ‘The Refractive Index of Gases and Vapours in a Magnetic Field Philosophical Magazine 1926 1 885 890 Thomson and Fraser, ‘The Process of Quantization’, ibid., 3 (1927), 1294–305; Fraser, ‘The Effective Cross Section of the Oriented Hydrogen Atom’, Proceedings of the Royal Society of London, A114 (1927), 212–21. The first paper reports the negative results of an experimental search for the magnetic-field induced, but field-strength independent, double refraction or alteration of refractive index that, as Stern had pointed out, was implied by the Bohr-Sommerfeld picture of space quantization. (Where previous experiments, using sodium resonance radiation, had shown the absence of such effects in the immediate neighbourhood of the Na D lines, Fraser illuminated sodium vapour with the mercury green line.) The second paper is theoretical, employing Bohr's correspondence principle in its elaborated, Fourier amplitude, form, together with measurements, by others, of pressure broadening of spectral lines, to construct a detailed, space-time, account of the establishment of the putative periodic orbit that is the stationary state. The third paper, describes a relatively crude but ingenious atomic beam experiment that failed to confirm the reality of space quantization as orientation of electron orbits — prompted, as was the first paper, at least as much by Glaser's claim to have observed such effects as by Stern's failure to find them. With an 1851 Exhibition Senior Studentship, Fraser spent some time in Munich late in 1926, proceeding to Hamburg at a date unknown. When Rabi arrived late in 1927 he found Fraser working on the electric moment of HCl, i.e. at the interface between physics and chemistry. In spring 1929, I. C. I. gave Fraser a good salary and a huge equipment grant to head a Molecular Beam Section of a Laboratory of Physical Chemistry they were setting up in Cambridge.
  • Columbia's . 1926 . Summer Session Announcement , : 104 – 104 . had Page teaching ‘Quantum Theory’, at 11:30 daily, and proposing to cover ‘Postulates of the Bohr Theory, Hamilton-Jacobi Partial Differential Equation, Conditionally Periodic Systems, Correspondence Principle, Theory of Fine Structure, Stark Effect, Zeeman, Effect, band spectra’. It is also possible that Rabi was among the auditors of the course on crystal optics that Rudolf Minkowski was then presenting at Hamburg — Vorlesungsverzeichnis for winter semester 1927/28 published in Physikalische Zeitschrift, 28 (1927), 742 — and in this way came to be reminded once again of that analogy.
  • Rabi . 1929 . Refraction of beams of molecules . Nature , 123 : 163 – 164 . Rabi, ‘Zur Methode der Ablenkung von Molekularstrahlen’, Zeitschrift für Physik, 54 (1929), 190–7. The title Rabi gave to his notice in Nature was doubtless intentionally (and misleadingly) playing on the then intense and widespread interest in de Broglie waves — not only the results that were just then beginning to emerge from Stern's laboratory, but more particularly those of Davison at Bell Telephone Laboratories, back home in New York City. Indeed, a letter properly on this subject begins on the same page of Nature on which Rabi's ends.
  • ‘Let the beam be in the plane of symmetry between the pole pieces’. ‘Since there is no component of the force parallel to the edge of the pole piece, we have as in the optical case …’ Rabi Refraction of beams of molecules Nature 1929 123 163 163
  • Rabi . 1929 . Refraction of beams of molecules . Nature , 123 : 164 – 164 . Initially, Rabi had thought there was much more than just this in his idea. ‘I have been fortunate enough’, he wrote Pegram, 14 December 1927 (CU, PP, box 8, fldr: R-Misc), ‘to hit upon an experimental method which not only greatly simplifies the whole procedure and practically removes the chief source of error in those molecular ray experiments but also increases the sensitivity almost hundred fold. (Having written these last three words, Rabi struck them out before sending the letter.) The new method utilizes the total change in energy in the field for the deflection, therefore the greater sensitivity. The reason for the greater accuracy is that a knowledge of the inhomogeneity is not required’. Of Rabi's claim to increased sensitivity — which he is here already beginning to moderate — no more will be heard, either in Stern's very strong statement in support of the ‘neue von Herrn Rabi erdachte Ausführungsform der Molekularstrahlmethode’ (Stern to Pegram, 21 January 1928, loc. cit.) or in the subsequent publications. Rabi's claim of increased sensitivity in consequence of the (angular) deflection of an atom bearing a magnetic moment μ depending on its total energy change μH on entering the uniform magnetic field H, is hard to understand, since with the conventional method the (angular) deflection depends on μ∇Hl, where l is the length of the deflecting field, and ∇ and l each easily contributes another factor of ten to the deflection. Perhaps, however, Rabi reasoned (logically, but impractically) that the additional factor of tanϑ on which in his method the angular deflection also depends, could be made arbitrarily large by making the glancing angle 90°-ϑ arbitrarily small.
  • Rabi . 1962–63 . draft of application for Guggenheim fellowship, November 1927.
  • Stern to Tisdale W.E. IEB 1927 December 12 (note 69). Rabi (1962–3), 93, in his earliest recorded recollections stated that Stern ‘at first did not care for the idea but became enthusiastic’. In subsequent recollections Rabi made no mention of Stern's initial reservations. A suggestion that Fraser played an important role in reversing Stern's initial coolness is contained in a letter of recommendation that Rabi wrote for him, 15 June 1936 (LC, RP, box 3, fldr 10): ‘I remember with gratitude that it was largely through his influence that I entered the field of molecular beams’. Cf. note 136.
  • Rabi to Pegram December 1927 14 and Pegram to Rabi, 30 December 1927 (CU, PP, box 8, fldr: R-Misc).
  • Rabi to Pegram (c. January 1928 24 (CU, PP, box 8, fldr ‘R-misc’). This letter, which Rabi neglected to date, is datable within a day or two by Bohr's presence just then in Hamburg: Bohr was scheduled to arrive on the 22nd ‘for a few days’ en route home from Switzerland. Bohr to Pauli, 8 January 1928, in Pauli (note 20), Wiss. Briefw., I, 421. It is from this letter that Kevles (note 2), The Physicists (1978), 201, quoted Rabi's observation that ‘When Bohr is about, everything is somehow different. Even the dullest gets a fit of brilliancy,’ dating it shrewdly as January 1928, but implying that it is from/about Copenhagen. Rigden (note 5), Rabi (1987), 58, took the quote from Kevles but ignored his dating, representing it as written during Rabi's stay in Copenhagen, 1927 September/October.
  • Rabi to Pegram March 1928 22 (CU, PP, box 8, fldr ‘R-misc’). The previous letter of c.24 January, speaks of a ‘preliminary apparatus’ and of it being constructed by the glassblower — and not the, less able, mechanic — while the present letter does not so qualify the apparatus and clearly implies that its construction is in the hands of the mechanic. The final, published, apparatus was indeed made of metal, the mechanic's medium. But inasmuch as metal apparatus was an innovation in Stern's Hamburg laboratory, due largely to Taylor, I surmise that initially a glass apparatus was designed for Rabi's experiment, but that before it came to be constructed, the research plan was changed to eliminate the preliminary apparatus and to duplicate Taylor's metal apparatus.
  • Rabi to Pegram March 1928 22 (CU, PP, box 8, fldr ‘R-misc.’).
  • Rabi . 1929 . Refraction of beams of molecules . Nature , 123 : 163 – 164 . Zs. f. Phys., 54 (1929), 196, says that ‘Im wesentlichen ist der Apparat (Fig. 6) derselbe wie in’ Taylor's experiments, and, further, that ‘Der einzige Unterschied gegenüber dem Taylorschen Apparat war der, dass Ofenraum und Auffangsraum nicht durch Messingröhrchen, sondern durch ein Messingstück 25 × 2·2 mm2 verbunden waren (12, Fig. 6)’. While the first quotation might be understood to mean that Rabi literally used the same apparatus that Taylor had used, the second quotation shades the meaning rather more toward Rabi's being a different apparatus but very similar in design.
  • Rabi . 1962–3 . : 93 – 95 . Rabi (December 1963), 22.
  • ‘My congratulations to your splendid success of the method of your own. It is a nice picture you sent me’. Y. Nishina in Paris to Rabi October 1928 21 (LC, RP, box 6, fldr 4); Rabi, notebook with date ‘July 31’ on first page and last entry dated ‘November. 28’ (LC, RP, box 75, fldr 2); typescript draft of Rabi (note 121) ZsP, 54 (1929), 190, with equations in Fraser's hand (LC, RP, box 62, fldr 12); Fraser in Hamburg to Rabi, 25 February 1929 (LC, RP, box 3, fldr 10), is reading Rabi's proofs and correcting his German, his exposition, and his choice of symbols. For Rabi's whereabouts through August 1929 the best source is his file in the records of the IEB (note 69).
  • Rabi . 1963 . December : 21 – 23 . Rabi (13 October 1975), 79.
  • Rabi to Pegram March 1929 15 (CU, PP, box 8, fldr ‘R-misc.’).
  • Meissner , W. and Scheffers , H. 1933 . Präzisionsbestimmung der magnetischen Momente von Kalium und Lithium in Hinblick auf ihr magnetisches Kernmoment, I/II . Physikalische Zeitschrift , 34 : 48 – 53 . 245–52. The damning critique of Rabi's method is in part II. As a method of electric deflection. Rabi's method did indeed have some technical advantages. Fraser sought to put it into practice right there and then, and Estermann too a year later, but the success was very moderate: I. Estermann and R. G. J. Fraser, ‘The Deflection of Molecular Rays in an Electric Field: The Electric Moment of Hydrogen Cloride’, Journal of Chemical Physics, 1 (1933), 390–9.
  • Bohr to Tisdale, IEB, 4 February 1928 (note 69): ‘I have just returned from a visit to Hamburg, where I met with Professor Stern, who expressed himself with great appreciation about a new idea of Dr. Rabi which promises a considerable improvement of the accuracy with which atomic magnetic moments can be measured by the famous Stern-Gerlach method’. Estermann I. Physikalische Berichte 1929 10 abstract of Rabi's U.z.M. in 1920–1 Rodebush (note 27), Rev. Mod. Ph., 3 (1931), 400–1, Stoner (note 84), Magnetism and Matter (1934), 221. Fraser (note 27), Mol. Rays (1931), 117–119, 150–152, was enthusiastic about Rabi's ‘absolute’ method, declaring (p. 150) that ‘Two notable advances in the technique of the deflection method were made in 1929. The first is due to Rabi, who showed that it was possible to replace the exceedingly difficult measurements of the inhomogeneity from point to point of the field by the determination of field strengths only; the second is the application by Taylor of Langumir and Kingdon's surface ionisation gauge to the quantitative measurement of alkali metal beams’.

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