SUBLEVEL SPECTROSCOPY OF ALKALI ATOMS IN SUPERFLUID-HELIUM

We report the results of optical pumping and optical detection of magn etic resonance of alkali atoms (Cs and Rb) in superfluid helium. The m agnetic resonances between the ground-state Zeeman sublevels and hyper fine levels are observed through monitoring the D-1 fluorescence by me ans of the optical-rf double resonance technique. Although the ground state g values in superfluid helium are the same as in vacuum within t he experimental error, the hyperfine constant of the ground state of t he Ca atom in superfluid helium is found to be slightly larger than in vacuum. Coherent transient spectroscopy is also performed.