Generalized Nikitin model: strong-coupling approximation

Abstract

The Delos-Thorson-type generalization of the exponential model of Nikitin in the two-state theory of atomic collisions is presented. The generalized Nikitin model defines a class of pairs of energy differences and couplings of which the original Nikitin model is a particular case. The transition probability is expressed in terms of the confluent hypergeometric function. It is shown that the generalized Nikitin model has the same peculiarity found recently in the generalized Demkov model: to derive the correct leading term of the strong-coupling asymptotic expansion of the transition probability, it is necessary to go beyond the leading terms of the strong-coupling expansions of the confluent hypergeometric functions involved. The strong-coupling approximation to the transition probability has all the correct limits and is shown to be very accurate in wide ranges of values of the free parameters.