On the basis of impulse approximate method, an analytical wavefuction based on a potential model was used to calculate the l-mixing transition cross section of Rydberg state Na atom in thermal collision with He, Ne and Ar, the results for Na-He are better than that of other methods ever used.
We have presented a theoretical description of J-mixing (the transfer of excitation between fine structure) cross sections of a Rydberg Cs atom induced by thermal collisions with noble-gas atoms. The theory is based on the application of impulse approximation theory and a kind of model-potential wave function. The results agree well with available recent experimental values for He, Ne, and Ar atoms. But for the heavier noble-gas atoms Kr and Xe, the theoretical cross sections are larger than the experimental ones.
Coupled-channel calculations for collisions of Na Rydberg atoms with He and Ar have been performed to investigate the effect of the interaction between the Na + core and the rare gas. For n=10, channels corresponding to the levels nd and nf are included, and calculations are reported both with and without terms arising from the core. It is found that the inelastic cross sections (10 to 10f) are insensitive to the core interactions, whereas the elastic cross sections (10d to 10d) may change significantly. This result is consistent with the prediction of the first-order Born approximation.
Semiclassical calculations of the quasi-elastic l-mixing and inelastic n,l-changing processes in thermal collisions of a Rydberg sodium atom with rare-gas atoms (Ne, Ar, Kr and Xe) as well as and atoms with Ne are presented in a wide range of principal quantum numbers. The main emphasis is put on the study of the effects in the Rydberg-atom - rare-gas-atom collisions associated with both the short- and long-range (polarization) parts of the electron - perturber interaction. It is shown that the polarization interaction between the highly excited electron and the Ne atom provides the major contribution to the cross section of the l-mixing and n, l -changing transitions. We show that the Ramsauer - Townsend effect in slow electron scattering by the heavy rare-gas atoms significantly affects the values of the cross sections, particularly for the inelastic transitions with large energy transfer. A quantitative explanation of these phenomena is given using the recently developed semiclassical normalized perturbation theory for the Rydberg-atom - neutral collisions combined with the modified effective range theory for scattering of slow electrons by the rare-gas atoms.