Rutherfords alpha-teilchen

References

• Rutherford , E. 1909 . “ The Chemical Nature of the a-Particles From Radioactive Substances ” . In Les Prix Nobel en 1908 11 – 11 . Stockholm ‘It is somewhat unexpected that the atom of a monatomic gas like helium should carry a double charge. It must not however be forgotten that the a-particle is released at a high speed as a result of an intense atomic explosion, and plunges through the molecules of matter in its path. Such conditions are exceptionally favourable to the release of loosely attached electrons from the atomic system.’ Sir James Chadwick (Ed.), The Collected Papers of Lord Rutherford of Nelson, Bd. ii, London 1963, S. 145, danach nur als C.P.R., ii zitiert.
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• Giesel , F. 1899 . Über die Ablenkbarkeit der Becquerelstrahlen im magnetischen Felde . Annalen der Physik , 305 : 834 – 836 . Über Giesel, vgl. Dictionary of Scientific Biography, 1972, 5, 394–395. Die Vorgeschichte dieser Entwicklung steht ausführlich bei W. Gerlach, ‘Die Analyse der Kathodenstrahlen in den Jahren 1893 bis 1899’, Nova Acta Leopoldina, Neue Folge, 1963, 27, 295–316. Ein Briefwechsel zwischen Giesel, Elster und Geitel, und St. Meyer und E. von Schweidler über Ablenkerfahrungen während der Monate Oktober und November 1899 ist bei St. Meyer, ‘Zur Geschichte der Entdeckung der Natur der Becquereltrahlen’, Die Naturwissenschaften, 1949, 36, 129–132, zu finden.
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• Trenn , T.J. 1971 . Rutherford and Soddy: From a Search for Radioactive Constituents to the Disintegration Theory of Radioactivity . Rete , 1 : 51 – 70 .
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• Heilbron , J.L. 1968 . The Scattering of a and β Particles and Rutherford's Atom . Arch. Hist. Exact Sci. , 4 : 247 – 307 .
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• Gamow , G. 1928 . Zur Quantentheorie des Atomkernes . Zeitschrift für Physik , 51 : 204 – 212 . Vgl. N. Feather, Electricity and Matter, Edinburgh, 1968, S. 516.
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• Rutherford , E. 1919 . Collision of a-Particles with Light Atoms . Philosophical Magazine , 37 ( 6 ) : 586 – 587 . (=C.P.R., ii, S. 589–590). ‘From the results so far obtained it is difficult to avoid the conclusion that the long-range atoms arising from collision of a particles with nitrogen are not nitrogen atoms but probably atoms of hydrogen, or atoms of mass 2. If this be the case, we must conclude that the nitrogen atom is disintegrated under the intense forces developed in a close collision with a swift a particle, and that the hydrogen atom which is liberated formed a constituent part of the nitrogen nucleus. … The results as a whole suggest that, if a-particles … of still greater energy were available for experiment, we might expect to break down the nucleus structure of many of the lighter atoms.’
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• Trenn . Rutherford and Soddy 59 – 60 . Heilbron, op. cit., S. 250–252 hat erörtert, daß die Rutherfordsche Strahlen-Analogie nach der Bestätigung durch Giesel im Jahre 1899, daß die ß Strahlen keine Röntgenstrahlen sondern Kathodenstrahlen seien, nicht überleben konnte. Es gibt jedoch Beweise dafür, daß Rutherford diese Strahlen-Analogie zwischen ß-Strahlen und α-Strahlen nur erweitert hatte; d.h. die Kathodenstrahlen erzeugten primär Röntgenstrahlen, die selbst wiederum sekundäre Röntgenstrahlen hervorriefen. Allerdings konnte diese erweiterte Strahlen-Analogie sowieso nur bis Mai 1902 aufrechterhalten werden.
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• Soddy , F. 1902 . The Radioactivity of Uranium . Trans. Chem. Soc. , 81 : 864 – 864 . (London) ‘… the conclusion is reached that if the α-radiation … is a secondary phenomenon produced by the ß [radiation], it takes at least a year to decay to half life value. As this is not in accordance with what is known of the nature of excited radioactivity, the view cannot be regarded as probable.’
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• Rutherford , E. and Grier , A.G. 1902 . Deviable Rays of Radioactive Substances . Philosophical Magazine , 4 ( 6 ) : 325 – 325 . (=C.P.R., i, S. 466). ‘For brevity and convenience we will call the non-deviable rays of all radioactive substances α rays, and the deviable rays ß rays.’ Arthur Gordon Grier war damals Assistent bei Rutherford.
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• Rutherford bevorzugte das Wort ‘erregt’ statt des damals von den Curies eingeführten Wortes ‘induziert, weil er vermutete, daß dieser Curiesche Ausdruck die Vorstellung erwecken könnte, der Effekt rühre in gewisser Weise von einer Wirkung durch das Medium hindurch her.; vgl. Rutherford Excited Radioactivity and the Method of its Transmission Philosophical Magazine 1903 5 6 95 95 (=C.P.R., i, S. 529). Die Curies bezweifelten, daß die Emanation materiell sei; vgl. M. Curie, Thesis, ‘Radio-active Substances’, Chemical News, 1903, 88, S. 236 und 247.
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• Rutherford , E. 1900 . Radioactivity Produced in Substances by the Action of Thorium Compounds . Philosophical Magazine , 49 ( 5 ) : 192 – 192 . (=C.P.R., i, S. 259). ‘… the difficulty is to advance a satisfactory reason for the particles obtaining the positive charge which they must possess in order to be moved to the negative electrode in an electric field’.
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• Rutherford , E. 1900 . Radioactivity Produced in Substances by the Action of Thorium Compounds . Philosophical Magazine , 49 ( 5 ) : 192 – 192 . (=C.P.R., i, S. 259). ‘On this supposition, the diminution of the amount of radioactivity on the negative electrode at low pressures is due to the fact that there is not a sufficient number of ions in the gas to charge the particles …’.
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• Rutherford , E. 1902 . Übertragung erregter Radioaktivität . Physikalische Zeitschrift , 3 : 214 – 214 . (=C.P.R., i, S. 357–358).
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• Rutherford , E. 1902 . Übertragung erregter Radioaktivität . Physikalische Zeitschrift , 3 : 214 – 214 . (=C.P.R., i, S. 358–359).
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• Rutherford . Excited Radioactivity and Transmission 112 – 112 . (=C.P.R., i, S. 544) eingegangen Juli 1902. ‘There is … considerable indirect evidence against the condensation hypothesis; and it has consequently been discarded in favour of [the view that] the particles of the emanation possess the property of expelling from themselves a negatively charged body of some kind. The particle would thus be left with a positive charge, and would be carried to the cathode by the electric field.’
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• Rutherford . Excited Radioactivity and Transmission 109 – 109 . & 114 (=C.P.R., i, S. 541 & 546). ‘The remaining 5 per cent must … reach the clectrode by other agencies. … It … seems likely that some of the radioactive carriers have sufficient initial velocity to carry them to the electrode against the electric field … This velocity is due to the recoil consequent upon the projection of the charged body.’ Hier ist das Wort ‘recoil’, d.h. Rückstoß, zum ersten Male in solch einem Zusammenhang gebraucht.
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• Rutherford . Excited Radioactivity and Transmission 114 – 114 . (=C.P.R., i, S. 545–546). ‘I have … made a close examination of the radiation from the emanation by the electrical method, but was unable to detect the presence of any … deviable rays. … if the rays are deflectible, the deviation is minute compared with the ß rays. This is to be expected if the mass of the expelled particle is large compared with the electron.’
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• Trenn . Rutherford and Soddy 68 – 68 . vgl. T. J. Trenn, The Nature of Rutherford's Alpha Rays, London (im Druck).
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• Rutherford , E. 1904 . Radio-Activity 283 – 283 . Cambridge Diese Verdichtungshypothese fehlt aber in der zweiten Auflage, Cambridge, 1905, S. 318–319, übersetzt von Emil Aschkinass, Die Radioaktivität, Berlin, 1907, S. 328. Rutherford benutzt stattdessen wieder eine Rückstoßhypothese.
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• Trenn , T.J. Rutherford and Recoil Atoms: The Metamorphosis and Success of a Once Stillborn Theory . Historical Studies in the Physical Sciences , 5 (im Druck)
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• Hahn , O. 1909 . Über eine neue Erscheinung bei der Aktivierung mit Aktinium . Physikalische Zeitschrift , 10 : 86 – 86 .
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• Kohlrausch , K.W.F. 1928 . Radioaktivität, in ‘Handbuch der Experimentalphysik’ Vol. XV , 647 – 648 . Leipzig herausgegeben von W. Wien und F. Harms
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• Rutherford , E. 1904 . The Succession of Changes in Radioactive Bodies . Philosophical Trans. Roy. Soc. , 204 : 212 – 212 . (=C.P.R., i, S. 716). ‘There is no doubt that the α particle behaves as a positively charged body, inasmuch as it is deviated in a magnetic and electric field in the opposite direction to the β particle. The failure to detect the charge carried by the α rays is probably due in part to a strong secondary ionization set up by the α rays …’
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• Rutherford , E. 1905 . Charge carried by the α Rays from Radium . Nature , 71 March : 414 – 414 . (=C.P.R., i, S. 790). ‘… these experiments undoubtedly show that the α particles do carry a positive charge, and that the previous failures to detect this charge were due to the masking action of the large number of slow-moving electrons …’.
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• Rutherford , E. 1905 . Charge carried by the α and β Rays of Radium . Philosophical Magazine , 10 ( 6 ) : 200 – 200 . (=C.P.R., i, S. 822), eingegangen Mai 1905. ‘There does not … now seem any doubt that the α particle is charged at the moment of its expulsion. The pressure of the gas in the experiments was so low that only a small fraction of the α particles could come into collision with the gas molecules … On the other hand, the magnitude of the charge carried by the α rays was independent of the state of the vacuum over a considerable range … We may thus conclude that … there is no obvious reason for supposing that they are not charged at the moment of their expulsion …’.
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• Rutherford , E. 1905 . Some Properties of the α Rays from Radium . Philosophical Magazine , 10 ( 6 ) : 169 – 169 . (=C.P.R., i, S. 808), eingegangen 8. Mai 1905.
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• Rutherford , E. 1906 . Magnetic and Electric Deflection of the α Rays from Radium . The Physical Review , 22 : 123 – 123 . (=C.P.R., i, S. 853). Vorgelegt in der Sitzung der American Physical Society, 29. Dezember 1905. Vgl. L. Badash (Ed.), Rutherford and Boltwood: Letters on Radioactivity, New Haven, 1969, S. 107.
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• Rutherford , E. 1906 . The Mass and Velocity of the α Particles Expelled from Radium and Actinium . Philosophical Magazine , 12 ( 6 ) : 358 – 358 . (=C.P.R., i, S. 889), eingegangen 20. Juli 1906.
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• Rutherford , E. and Robinson , H. 1913 . “ Über die Masse und die Geschwindigkeiten der von den radioaktiven Substanzen ausgesendeten α-Teilchen ” . In Sitzungsberichte der Kaiserl. Akademie der Wissenschaften in Wien, Math.-naturw. Klasse Vol. 122 , 1878 – 1878 . in Abt. IIa (=C.P.R., ii, S. 401). Vgl. E. Rutherford, J. Chadwick, and C. D. Ellis, Radiations from Radioactive Substances, Cambridge 1951, [1930] S. 41 & 46.
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• Rutherford , E. 1908 . Recent Advances in Radio-activity . Nature , 77 : 425 – 425 . (=C.P.R., ii, S. 67–68). Vortrag an der Royal Institution, London, am 31 Januar 1908 vorgelegt. ‘The value of e/m found by experiment is nearly 5 × 103. Now the value of e/m for the hydrogen atom in the electrolysis of water is 104. If the charge carried by the α particle and the hydrogen atom is the same, the mass of the α particle is twice that of the hydrogen atom, i.e. a mass equal to the hydrogen molecule. But we are not certain that they do carry the same charge. Here we are, unfortunately, confronted by a number of possibilities, for the magnitude of m for the α particle is conditioned by the value assumed for e. If the charge of the a particle is assumed to be twice the value of the hydrogen atom, the mass comes out four times the hydrogen atom—the value found for the helium atom.’
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• Trenn , T.J. Rutherford's Electrical Method: Its Significance for Radioactivity and an Expression of his Metaphysics . Actes XIIIe Congrès International d'Histoire des Sciences . (im Erscheinen)
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• Rutherford , E. and Geiger , H. 1908 . An Electrical Method of Counting the Number of α-Particles from Radio-active Substances . Proc. Roy. Soc., London , 81-A : 141 – 141 . (=C.P.R., ii, S. 89), vorgelegt in der Sitzung am 18. Juni 1908. ‘The need of a method of counting the α-particles directly without any assumption of the charge carried by each has long been felt … If the number of α-particles expelled from a definite quantity of radio-active matter could be determined by a direct method, the charge carried by each particle could be at once known by measuring the total positive charge carried by the α-particles. In this way, it should be possible to throw some light on the question whether the α-particle carries a charge e or 2e, and thus settle the most pressing problem in radio-activity, viz., whether the α-particle is an atom of helium.’
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• Zuerst beobachtete Giesel den Effekt der α-Strahlen an einem Zinksulphid-Schirm, in Über den Emanationskörper aus Pechblende und über Radium Berichte der Deutschen Chemischen Gesellschaft 1903 36 342 347 wiederveröffentlicht in Chemical News, 27. Februar 1903, 87, 97–98. Er nahm den Zinksulphid-Schirm auch als Mittel, um α von β Strahlen unterscheiden zu können, ‘Über Polonium’, Berichte der Deutschen Chemischen Gesellschaft 1903, 36, 728–729, wiederveröffentlicht in Chemical News, 20. März 1903, 87, 133. Sein szintillierender Effekt wurde auch von J. Elster und H. Geitel beobachtet, ‘Über die durch radioaktive Emanation erregte szintillierende Phosphoreszenz der Sidotblende’, Physikalische Zeitschrift, 1. Mai 1903, 4, 439, eingeg. 27. März 1903. W. Crookes, der als Herausgeber der Zeitschrift Chemical News Bescheid wusste, berichtete in seiner Vorlesung vor der Royal Society am 19. März 1903 über diesen Effekt: ‘The Emanations of Radium’, Proc. Roy. Soc., 1903, 71, 405–409; er führte das ‘Spinthariscope’ ein, in ‘Certain Properties of the Emanations of Radium’, Chem. News., 22. Mai 1903, 87, 241.
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• Regener , E. 1908 . Über Zählung der α-Teilchen durch die Szintillation und die Größe des elektrischen Elementarquantums . Verhandlungen der Deutschen Physikalischen Gesellschaft , 10 : 78 – 83 . Erich Regener (1881–1955) schloß sein Studium 1905 in Berlin mit der Promotion bei E. Warburg ab. Zusammen mit E. Meyer im Jahre 1908 arbeitete er über radioaktive Schwankungen. 1909 habilitierte er sich in Berlin mit einer Arbeit über die Zählung der radioaktiven α-Teilchen durch Szintillationsbeobachtung und die gleichzeitige Messung der von ihnen mitgeführten positiven Ladung, welche zur ersten direkten Bestimmung des Wertes des elektrischen Elementarquantums führte. Zwischen 1913 und 1920 war er Professor am physikalischen Institut der Landwirtschaftlichen Hochschule in Berlin; seit 1920 lehrte er an der Technischen Hochschule Stuttgart. Quelle: W. Gerlach, ‘Erich Regener’, Jahrbuch der Bayerischen Akademie der Wissenschaften, 1956, S. 222–229.
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• Rutherford and Geiger . Electrical Method 61 – 61 . (=C.P.R., ii, S. 108).
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• Rutherford , E. and Geiger , H. 1908 . The Charge and Nature of the α-Particle . Proc. Roy. Soc. , 81 : 162 – 162 . (=C.P.R., ii, S. 109); vorgelegt in der Sitzung am 18. Juni 1908. ‘Knowing this number, the charge carried by each particle can be determined by measuring the total charge carried by the α-particles expelled per second from a known quantity of radium.’
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• Rutherford , E. and Geiger , H. 1908 . The Charge and Nature of the α-Particle . Proc. Roy. Soc. , 81 : 162 – 162 . (=C.P.R., ii, S. 109). Vgl. Rutherford, ‘Charge by α and β Rays’, 193–208 (=C.P.R., i, 816–829).
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• Die Ionisation wurde begrifflich mit nur einer Ladungseinheit verknüpft. W. Makower schrieb in The Radioactive Substances, London 1908; ‘… if the α particle carries this double charge, it is a remarkable fact and would be quite unique, for it will be remembered that in the case of the ions in a gas produced by various ionizing agents, the charge was always found to be that carried by the hydrogen ion in electrolysis’. S. 82. ‘Wenn das α-Teilchen zwei solcher Ladungseinheiten tragen würde dann, wäre diese Tatsache sehr bemerkenswert und ganz einmalig. Denn erinnern wir uns, dass im Falle der Gasionen, welche durch verschiedenste ionisierende Ursachen erzeugt werden, die Ladung stets gleich der eines Wasserstoffions bei Elektrolyse war’. Vgl. Millikan R.A. The Electron Chicago 1963 140 140 [1917],
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• Rutherford and Geiger . Charge and Nature 168 – 171 . (=C.P.R., ii, S. 115–118). Als Standardwerte für die Ladung galten damals 3, 4.10-10 esE (J. J. Thomson 1903) bzw. 3,1.10-10 esE (H. A. Wilson). Das Ergebnis 4,65.10-10 esE von Rutherford liegt etwa 30% höher als der Thomsonsche Wert, d.h. (4·65-3·40)/[(4·65 + 3·40)/2] = 31% und rund 14% höher als der anfängliche Wert 4,03 × 10-10 esE von R. A. Millikan, ‘On the Charge Carried by the Negative Ion of an Ionized Gas’, Physical Review, Februar 1908, 26, S. 198. Ein moderner Wert ist 4,803.10-10 esE, vgl. J. A. Crowther, Ions Electrons and Ionizing Radiations, achte Auflage, London 1949, S. 48.
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• Rutherford and Geiger . Charge and Nature 171 – 171 . (=C.P.R., ii, S. 118); vgl. M. Planck, ‘Zur Theorie des Gesetzes der Energieverteilung im Normalspectrum’, Verhandlungen der Deutschen Physikalischen Gesellschaft, 1900, 2, S. 245.
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• Rutherford . Recent Advances 425 – 425 . (=C.P.R., ii, S. 68). ‘… if the charge carried by the α particle could be experimentally determined, the actual value of m could be determined in terms of the hydrogen atom …’.
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• Rutherford , E. and Geiger , H. 1908 . An Electrical Method of Counting the Number of α-Particles from Radio-active Substances . Proc. Roy. Soc., London , 81-A : 141 – 141 .
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• Rutherford , E. and Soddy , F. 1902 . The Cause and Nature of Radioactivity: Part II . Philosophical Magazine , 4 : 582 – 582 . (6) (=C.P.R., I, S. 506).
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• Ramsay , W. and Soddy , F. 1903 . Gases Occluded by Radium Bromide . Nature , 68 : 246 – 246 . 16, Juli
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• Rutherford , E. 1903 . The Amount of Emanation and Helium from Radium . Nature , 68 : 366 – 366 . 20. August (=C.P.R., i, S. 610). ‘The determination of the mass of the α body, taken in conjunction with the experiments on the production of helium by the emanation, supports the view that the α particle is in reality helium’.
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• Rutherford , E. 1905 . Some Properties of the α Rays from Radium . Philosophical Magazine , 10 ( 6 ) : 169 – 169 .
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• Mackenzie , A.S. 1905 . The Deflexion of α Rays from Radium and Polonium . Philosophical Magazine , 10 : 545 – 545 . (6) eigengangen 31. Juli 1905. Arthur Stanley Mackenzie (1865–1938) war von 1894 bis 1904 Professor der Physik an dem Bryn Mawr College (U.S.A.) und von 1905 bis 1910 an der Dalhousie University, Halifax, Nova Scotia (Canada). 1904–1905 arbeitete er ein Jahr lang als Gastprofessor am Cavendish Laboratory in Cambridge, von 1910–1911 als Professor der Physik am Stevens Institute of Technology, New Jersey. 1911 wurde er Präsident der Dalhousie University.
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• Rutherford , E. and Robinson , H. 1913 . “ Über die Masse und die Geschwindigkeitender von den radioaktiven Substanzen ausgesendeten α - Teilchen ” . In Sitzungs berichte der Kaiserl. Akademie der Wissenschaften in wien, Math.-naturw. Klasse Vol. 122 , 1878 – 1878 . Abt. IIa,
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• Mackenzie . Deflexion 546 – 546 . Mackenzie arbeitete in dieser Zeit im Cavendish Labor mit J. J. Thomson und vertrat den traditionellen Gesichtspunkt, daß ein Ion nur eine Ladungseinheit besitzt, vgl. Fußnote 43 und vgl. J. J. Thomson, Conduction of Electricity through Gases, zweite Auflage, Cambridge 1906, S. 77.
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• Rutherford . Magnetic and Electric Deflection 123 – 123 . (=C.P.R., i, S. 853). ‘It is not at present possible to decide definitely … whether the α particle is a molecule of hydrogen, an atom of helium, or a helium molecule [both atoms] carrying twice the ionic charge’. Mackenzie hat die Idee geäußert, daß die α Teilchen ein Wasserstoffmolekül sein könnent, vgl. Fußnote 54
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• Rutherford . Mass and Velocity 365 – 365 . (=C.P.R., i, S. 895). ‘I think there can be no doubt that the α particles emitted from the various products of radium have an identical mass, but differ only in the initial velocities of projection … This is an important conclusion; for it shows that uranium, thorium, radium and actinium, which behave chemically as distinct elements, have a common product of transformation. The α particle constitutes one of the fundamental units of matter of which the atoms of these elements are built up’.
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• Rutherford . Mass and Velocity 365 – 366 . (=C.P.R., i, S. 895–896). ‘… the value of e/m for the hydrogen atom is 104. The observed value of e/m for the α particle is 5·1 × 103, or … one half of that of the hydrogen atom … If a helium atom carries the same charge as the hydrogen ion, the value of e/m for the helium atom should consequently be about 2·5 × 103. If we assume that the α particle carries the same charge as the hydrogen ion, the mass of the α particle is twice that of the hydrogen atom’. Vgl. A. van den Broek, ‘Das α-Teilchen und das periodische System der Elemente’, Annalen der Physik, 1907, 328, 199–203.
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• Rutherford . Mass and Velocity 367 – 367 . (=C.P.R., i, S. 896–897). ‘On this view, the α particle is in reality a helium atom which is either expelled with a double ionic charge or acquires this charge in its passage through matter. Even if the α particle were initially projected without charge, it would certainly acquire one after the first few collisions with the molecules in its path … If the α particle can remain stable with the loss of two electrons, these electrons would almost certainly be removed as a result of the intense disturbance set up by the collision of the α particle with the molecules of matter. The α particle would then have twice the normal ionic charge, and the value of e/m … would be quite consistent with the view that the α particle is an atom of helium’.
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• Rutherford , E. 1905 . Charge carried by the α and ß Rays of Radium . Philosophical Magazine , 10 : 200 – 200 . (6)
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• Rutherford and Geiger . Charge and Nature 172 – 172 . (=C.P.R., ii, S. 118). ‘an α-particle is a helium atom, or to be more precise, the α-particle, after it has lost its positive charge, is a helium atom’. Das α Teilchen ist hier als zweifach ionisiertes Edelgasatom angenommen.
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• Cameron , A.T. and Ramsay , W. 1907 . The Chemical Action of Radium Emanation, Part II: On Solutions Containing Copper, and Lead, and on Water . Journ. Chem. Soc., London , 91 : 1605 – 1605 .
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• Rutherford , E. and Royds , T. 1908 . The Nature of the α Particle . Memoirs of the Manchester Literary and Philosophical Society , 53 : 1 – 2 . (4) number 1 (=C.P.R., ii, S. 134); in der Sitzung am 3. November 1908 vorgelegt: ‘This evidence is, however, of too indirect a character to prove decisively that the α particle is an atom of helium. It might be possible, for example, that the expulsion of an α particle led to the liberation of helium from the active matter, but that the α particle itself was not an atom of helium’.
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• Vgl. Trenn The Nature of Rutherford's Alpha Radiation
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• Rutherford , E. and Royds , T. 1909 . The Nature of the α Particle from Radioactive Substances . Philosophical Magazine , 17 : 286 – 286 . (6) (=C.P.R., ii, S. 167) eingegangen 13. November 1908: ‘We can conclude with certainty from these experiments that the α particle after losing its charge is a helium atom’.
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• Rutherford , E. Chemical Nature of α-Particles 11 – 11 . (=C.P.R., ii, S. 145). ‘… that the α-particle is a projected atom of helium, which has, or in some way during its flight acquires, two unit charges of positive electricity … If the α-particle can lose two electrons … the double positive charge is explained’. Vgl. Fußnote 1.
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• Rutherford , E. 1907 . The Velocity and Energy of the α Particles from Radioactive Substances . Philosophical Magazine , 13 ( 6 ) : 117 – 117 . (=C.P.R., i, S. 916). ‘A study of radioactive phenomena has emphasized the importance of the α particle as one of the units of which the heavier atoms are built up, and it is not improbable that the α particle may play an equally important role in the constitution of other atoms besides those of uranium, thorium, radium, and actinium’.
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