Theory of coherences produced by radiatively assisted inelastic collisions: Weak-field impact-core limit

A theoretical calculation of the final-state coherences produced by a radiatively assisted inelastic collision (RAIC) is presented. Two atoms, $A$ and $A^{\prime }$, collide in the presence of an external radiation field to produce the RAIC reaction $A_i+A_{i^{\prime }}^{\prime }+\hslash \Omega \to A_f+A_f^{\prime }$, where $|{\mathrm{ii}}^{\prime }〉$ is the initial state, $|{\mathrm{ff}}^{\prime }〉$ is the final state, and $\Omega$ is the frequency of the external field. It is assumed that the final states consist of a number of nearly degenerate levels and the coherences produced in these levels by the RAIC reaction is calculated. These final-state coherences can be monitored by standard techniques (polarization of fluorescence, quantum beats) enabling one to use the final-state coherences as a probe of the RAIC reaction. The calculation is limited to the weak-field (perturbation-theory) limit and is valid only in the impact core of the RAIC profile.