Thermal collisions of high Rydberg atoms with neutral particles. I. General theory and modified impulse approximation

A general theoretical formulation of the Rydberg-atom-neutral-atom inelastic processes is presented in order to define precisely the physical content of the simple impulse picture and to develop a systematic correction procedure. A simple modification of the impulse amplitude is then introduced to incorporate the distortion effect caused by the presence of the core of Rydberg atom. A preliminary calculation provides a reasonable description of the inelastic scattering involving low principal quantum numbers as well.