Influence of the spin-orbit coupling on the optical collision for Ba atom perturbed by rare gases

The quant um non-adiabatic theory of atomic collisions in the presence of a weak radiation field is applied to describe the Ba-rare-gas (RG) optical c ollision. The absorption coefficient as well as linear and circular polariz ations of collisionally redistributed fluorescence light are calculated for a range of detuning around the barium (lambda = 5535 Angstrom) resonance l ine. Close-coupling calculations involving the relevant X(1)Sigma, (1)Sigma , (1)Pi, (3)Sigma and (3)Pi states for each Ba-RG pair are carried out base d on the new theoretical potential curves obtained by Czuchaj within the va lence ab initio scheme. Our attention is mainly paid to the role of spin-ch anging transitions between the (6s6p) P-1 and (6s6p) P-3 states in the proc ess investigated. The numerical results show that the singlet-triplet mixin g is import ant in the red-wing part of the spectra. The calculated absorpt ion coefficients and polarizations are thermally averaged over the collisio n energy and compared with the experimental results of Alford et al.