Polarization of thallium atoms produced in molecular photodissociation: experiment and theory

A study has been made of the oriented ground state Tl(6² P _1/2) atoms produced in the photodissociation of TlBr molecules by circularly polarized 266-nm laser light. A significant degree of atomic orientation (15%) has been measured in the experiment which corresponds to the initial degree of orientation of 37%. A high value of depolarization cross section (210 Ų) for the oriented Tl atoms colliding with TlBr molecules has been also observed. The obtained experimental results have been treated theoretically. We present a general quantum mechanical theory of the orientation phenomenon in which all possible nonadiabatic interactions as well as molecular rotation are properly treated. The application of the theory to the case of TlBr photodissociation allowed to understand the obtained experimental results and to evaluate the probability of the earlier unknown radial nonadiabatic transition in the decaying molecule.