The influence of the ionic core in Rydberg-atom–neutral collisions is evaluated within the framework of the impulse approach. It is shown that this contribution exhibits the same n behavior as that due to the Rydberg-electron–perturber interaction, though its magnitude is usually smaller. The general features of the core-perturber contribution are investigated. It is shown that there exists some situations for which effects ascribable to the core-perturber interaction are expected to be noticeable.

• Received 1 February 1985

DOI:https://doi.org/10.1103/PhysRevA.32.793