Abstract
The experimental fine and hyperfine structures of low Rydberg states with
2–4 measured in the 1970's for various vibration-rotation levels by Lichten and collaborators, and by Miller and Freund, are reanalysed in the framework of molecular frame-transformation multichannel quantum defect theory MQDT. Instead of the level by level treatment in terms of an effective Hamiltonian as was carried out at the time, a global theory is applied to all levels at once. It is found that the essence of the observed level patterns is well represented by MQDT in terms of a substantially reduced number of dynamical parameters – quantum defects – although the experimental accuracy of the experiments is not yet quite reached. Possible reasons for the remaining discrepancies are given. Since quantum defect theory MQDT, a formalism derived from scattering theory, is still rather little used in the domain of modern ultra-high precision spectroscopy, the occasion is taken here to review some of its key elements.
GRAPHICAL ABSTRACT
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Acknowledgements
The author wishes to thank Dr. Max Beyer (Amsterdam) for his helpful remarks on the manuscript.
Disclosure statement
No potential conflict of interest was reported by the author.