Eur. Phys. J. D (2014) 68: 368
https://doi.org/10.1140/epjd/e2014-50460-4

Regular Article

Collisional destruction of circular Rydberg states by atoms with small electron affinities

¹ P.N. Lebedev Physical Institute, Leninsky prospect 53, 119991 Moscow, Russia
² Moscow Institute of Physics and Technology (State University), Institutskií per. 9, Dolgoprudnyí, 141700 Moscow Region, Russia

^a e-mail: narits@sci.lebedev.ru

Received: 18 June 2014
Received in final form: 24 September 2014
Published online: 10 December 2014

Abstract

The results of theoretical studies of interaction between neutral targets with small electron affinities and Rydberg atoms in circular states are reported. The cross sections of collisional destruction of such states due to the resonant quenching mechanism are calculated on the basis of the semiclassical theory of nonadiabatic transitions between the ionic and Rydberg covalent terms of a quasimolecule combined with recently developed technique for exact evaluation of matrix elements. We obtain the basic formula for the square of the coupling parameter involving Rydberg nlm-state with the given values of the principal, orbital, and magnetic quantum numbers. It is employed for the derivation of explicit expressions for transitions from circular states applicable in cases of s- and p-states of negative ion temporarily formed during a collision of atoms. Numerical calculations are carried out for thermal collisions of Li^∗ and Na^∗ atoms with Ca(4s²) and Sr(5s²). We explore n-, l-, m-, and velocity-dependences of the cross sections and analyze orientation effects in such collisions. Cross sections of resonant quenching for circular states (l = | m | = n − 1) are shown to be much smaller than those for states with small l values and typically two times lower than for nearly-circular states (l = n − 1) averaged over m.