Collisional Effects on Induced Emmission and Absorption Transition Probabilities in Atomic Systems

Abstract

The transition probabilities for induced emission and absorption of electromagnetic radiation by an excited atom interacting, in addition to the radiation field, with a system of perturbers (in single, binary, and completed encounters) are evaluated. It is found that Dirac's result $\frac{{W}_{\mathrm{ind}}}{{W}_{\mathrm{abs}}}=\frac{({\overline{n}}_{l\ensuremath{\sigma}}+1)}{{\overline{n}}_{l\ensuremath{\sigma}}}$ must be modified by a factor $\frac{{(1\ensuremath{-}\ensuremath{\alpha}n)}^{2}}{{(1+\ensuremath{\alpha}n)}^{2}}$, where $\ensuremath{\alpha}$ is related to the interaction potential of the emitter-perturber system as well as to the level structure of the colliding atoms, and $n$ is the perturber number density.