The effect of core interactions in l-mixing collisions of Rydberg atoms with rare gases

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.