Simple analytical formulas for collisionallmixing,nchanging, and ionization of Rydberg atoms with neutral particles at thermal energy

Abstract

Simple analytical formulas are given that allow the rapid estimation of cross sections for $l$ mixing, $n$ changing, and ionization of Rydberg atoms with atomic and molecular targets. These formulas are derived by using the quasifree-electron model and the impulse approximation. The $l$ dependence of the cross section is accounted for only via the atomic energy. The quasielastic process of angular-momentum mixing caused by either the short- or long-range interaction between the Rydberg electron and the neutral perturber is studied and the corresponding cross sections are evaluated. The Rydberg-atom—molecule inelastic transitions ($n$ changing and ionization) caused by the $e^{-}$-dipole or $e^{-}$-quadrupole interaction are investigated. It is shown that the $n$-changing reactions occur via quasiresonant internal-energy transfer between the two colliding partners. The influence of the relevant physical parameters is clearly stated for the three types of interaction (short-range, $e^{-}$-dipole, $e^{-}$-quadrupole). Comparison with more sophisticated approaches and experimental data shows that the accuracy of the formulas is about a factor of 2.