Resonance ionization spectroscopy of high-lying 4sns and 4snd Rydberg levels of odd calcium isotopes

Calcium Rydberg levels are of significant interest for efficient and isotope-selective resonance ionization of trace radionuclides such as calcium-41 (41Ca). In this study, we report novel, to our knowledge, measurement data on the energy level shifts of 43Ca for 4sns 1S0 and 4s(n - 1)d 1D2 (n = 40, 45, 50, 55, 60) Rydberg levels due to hyperfineinduced singlet-triplet mixing specific to isotopes with an odd mass number. Both 3S1 and 3DJ triplet signals corresponding to forbidden transitions were enhanced for 43Ca at the high principal quantum numbers n = 55 and 60, indicating a mixing of singlet components to some extent. (c) 2023 Optica Publishing Group