Manifestation of higher polarization moments in the dipole emission under conditions of stepwise excitation and anisotropic collisions

The induction of higher polarization moments-the octupole orientation and t he hexadecapole alignment-in the case of two-step excitation of atoms throu gh dipole transitions and their manifestation in the polarization of dipole emission under conditions of anisotropic collisions are studied. For all c hannels of the two-step excitation process J(0) --> J(1) --> J, the efficie ncies of production of higher polarization moments with integer and half-in teger angular momenta from J = 2 to J = 7 through the absorption of linearl y or circularly polarized light are calculated. The rates of collisional re laxation and interconversion of higher polarization moments, for both orien tation and alignment, as functions of frequency detuning of the laser line from the center of the Doppler profile are calculated. The theory is illust rated by an example of two channels of excitation of the atomic state J = 2 by circularly polarized light: J(0) = 0 --> J(1) = 1 --> J = 2 and J(0) = 3 --, J, = 2 (or 3) --, J = 2. In the first case, the octupole orientation enhances or attenuates the signal of circular plarization depending on the laser frequency detuning. In the second case, it represents the only source producing orientation and circular polarization of the emitted light. (C) 2001 MAIK "Nauka/Interperiodica".