The Anderson Talman theory of spectral line broadening is used together with potential energy curves calculated at the spin-orbit multi-reference configuration interaction level to compute broadening, shifting, and asymmetry coefficients of the D1 and D2 lines of alkali-metal atoms M, as they collide with noble gas atoms N, where M=K, Rb, and Cs, and N=He, Ne, and Ar. Our calculated coefficients are compared to experimental results for a variety of temperatures. In all cases general agreement is observed for the broadening coefficients, while significant disagreement is observed for the shifting coefficients. We also compare our K+He broadening and shifting results with fully quantum-mechanical calculations that employ the Baranger theory of collisional line broadening, and we compare our results with other semiclassical calculations. As with the comparison to experiment, closer agreement is observed for the broadening coefficients while the shifting coefficients exhibit significant disagreement. We use the natural variation between the difference potentials of the nine M+N pairs to explore the relationship between potential and line shape as determined by Anderson-Talman theory and develop a picture for the mechanism that underlies the general agreement between theoretical and experimental results on the broadening coefficient and the general disagreement on shifting coefficients.
Physical Review A
Blank, L. A., & Weeks, D. E. (2014). Impact broadening, shifting, and asymmetry of the D1 and D2 lines of alkali-metal atoms colliding with noble-gas atoms. Physical Review A, 90(2), 022510. https://doi.org/10.1103/PhysRevA.90.022510