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].