Collisions of rubidium Rydberg-state atoms with ammonia

Total depopulation cross sections of Rb(ns) and Rb(nd) levels by collisions with NH₃ have been measured over a wide range of n values (24{≤}n{≤}49). The analysis of the n-dependent behavior of the cross sections reveals that NH₃ inversion can produce a very efficient l-mixing process via a quasiresonant mechanism. This behavior appears qualitatively well described by theoretical calculations based on the impulse approximation (IA). A quantitative comparison between theory and experiment appears difficult, but it seems that the IA should provide reasonable estimates (within a factor of 4), though its use for large dipole moment (1.47 D for NH₃) is questionable from a theoretical point of view.