Observation of a circular dichroism of an ensemble of triplet metastable helium atoms in a Na-He gas-discharge plasma with laser-oriented sodium atoms

We describe an experiment on the observation of a circular dichroism of an ensemble of triplet metastable helium atoms in a sodium-helium gas-discharge plasma where Na atoms are optically oriented with circularly polarized radiation of a laser tunable around the resonant sodium doublet (with wavelength of 589.0 and 589.6 nm, corresponding to the 3² S _1/2 ⇄ 3² P _1/2 and 3² S _1/2 ⇄ 3² P _3/2 transitions). Conditions of observation and the polarization degree of 2³ S ₁ atoms are determined.