Physical Review A
Level shifts ofmsnsRydberg states induced by hyperfine interaction in odd alkaline-earth isotopes
R. Beigang, Andre Timmermann
Abstract
High-resolution two-photon spectroscopy was applied to investigate the msns $^{1}S_{0}$ Rydberg states of the alkaline-earth elements Ca, Sr, and Ba. It is shown for $^{43}\mathrm{Ca}$, $^{87}\mathrm{Sr}$, $^{135}\mathrm{Ba}$, and $^{137}\mathrm{Ba}$ that the hyperfine interaction causes a level shift between odd- and even-mass isotopes. A theoretical interpretation is presented which relates the energy-level shift for odd isotopes to the singlet-triplet separation which in turn is a function of the principal quantum number, and good agreement with the experimental results is found.