Singlet-triplet mixing in4sndRydberg states of Ca

Abstract

Singlet-triplet mixing of $4snd ^{1}D_{2}$ and $^{3}D_{2}$ states of Ca was determined between principal quantum numbers $7<~n<~42$ with the use of Doppler-free two-photon spectroscopy. The hyperfine structure of the $4snd ^{1}D_{2}$ states was used to probe admixtures of triplet character into the singlet wave functions. It turned out that, in the region of series crossings, an enlarged singlet-triplet mixing was observed.