Simple analytical formulas for collisional<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>l</mml:mi></mml:math>mixing,<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>n</mml:mi></mml:math>changing, 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 ${e}^{\ensuremath{-}}$-dipole or ${e}^{\ensuremath{-}}$-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, ${e}^{\ensuremath{-}}$-dipole, ${e}^{\ensuremath{-}}$-quadrupole). Comparison with more sophisticated approaches and experimental data shows that the accuracy of the formulas is about a factor of 2.