Depolarization mechanisms in alkali-noble gas half collisions

The polarization properties of excited alkali atoms having suffered half collisions with noble gas atoms following excitation by nonresonant photon absorption during a strong collision, are investigated. On the basis of a semiclassical perturbation treatment of the density matrix up to second order in the driving field a general expression for the polarization dependent intensity of the emitted alkali fluorescence is derived. Assuming quasistatic excitation of the collision complex and considering reorientation of the orbital and spin electronic angular momenta within a cut off radius, explicit results for the polarization degrees are presented and discussed, depending on the initial molecular excited state and coupling case.