Wirkungsquerschnitte depolarisierender Stöße von angeregten Natriumatomen mit Edelgasatomen durch optisches Pumpen mitD ₂-Licht

Abstract

Optical pumping of sodium vapor withD ₂-light causes a rise of optical transparency if complete collision-induced mixing takes place among the sublevels of the excited² P-states. It causes a drop of optical transparency if there would be no mixing in the excited states. It causes no change of optical transparency if excited-state mixing is as strong as the condition 2T=3τ predicts,T being the mean collision time, τ the mean life time of the excited states. The latter case can be realized by certain buffer gas pressures. These pressures have been measured for the gases helium, neon, and argon. From these pressures excited state-mixing cross sections have been deduced by means of the quoted condition. Finally the so far used “uniform” mixing model has been critically revised. A more realistic model is proposed which ascribes excited-state-mixing to scattering phase shifts between the molecularσ- andπ-states into which the atomic² P-state splits during the collision. Nevertheless, the condition 2T=3τ is not seriously altered even in this refined model.