Validity of the impulse approximation in Rydberg-neutral collisions

The validity of the impulse approximation (IA) in thermal Rydberg-neutral collisions rests critically on the semiclassical nature of the Coulomb binding potential. The authors have shown that the IA is valid in both thermal and high-Rydberg-neutral collisions by estimating the second-order terms of the IA. The authors have also indicated that the thermal quasielastic state-changing collisions of the high-Rydberg atoms with the neutrals can be viewed as proceeding via the Rydberg electron-neutral encounters. The core effect proposed by Flannery (1982) is shown to be unimportant for the case of thermal quasielastic Rydberg-neutral collisions.