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

The quantum non-adiabatic theory of atomic collisions in the presence of a weak radiation field is applied to describe the Ba-rare-gas (RG) optical collision. The absorption coefficient as well as linear and circular polarizations of collisionally redistributed fluorescence light are calculated for a range of detuning around the barium (λ₃ = 5535Å) resonance line. Closecoupling calculations involving the relevant X¹Σ, ¹Σ,¹II, ³Σ and ³II states for each Ba-RG pair are carried out based on the new theoretical potential curves obtained by Czuchaj within the valence ab initio scheme. Our attention is mainly paid to the role of spin-changing transitions between the (6s6p) ¹P and (6s6p) ³P states in the process investigated. The numerical results show that the singlet-triplet mixing is important in the red-wing part of the spectra. The calculated absorption coefficients and polarizations are thermally averaged over the collision energy and compared with the experimental results of Alford et al. 1984, Phys. Rev. A, 30, 2366] and Ni et al. 1996, Z. Phys. D, 38, 303].