Laser Induced Collisions

Abstract

If the energy defect of an atomic process ΔE is large with respect to kT , then the cross section for collision or chemical reaction will be quite small. In this paper we consider collision processes where one or more photons are utilized to conserve energy, i.e., nħω ≅ ΔE. A proto-type system is shown in Fig. 1. Energy is first stored in the designated s state of the A atom. During collision of the A and B atoms an electromagnetic field at frequency ħω causes the A atom to make a virtual transition. Long range dipole-dipole coupling between the two atoms causes this excitation to be transferred to the B atom to complete the excitation. Energy transfer is thus initiated or “switched” by the presence of the optical radiation. The possibility of collision processes of this type have been predicted by GUDZENKO and YAKOVLENKO [1] and by HARRIS and LIDOW [2]. Recent theoretical work is given by PAYNE and NAYFEH [5], GELTMAN [4], and GEORGE, et al. [5]. Though an apparently successful experiment recently reported by LIDOW, et al. [6] is now in question, we report additional experimental results which we believe demonstrate a laser induced collision.

We describe processes where one or more photons are utilized to conserve energy between the initial and final states of colliding atoms. Energy transfer is thus initiated, and directed to particular states, by the optical radiation. We report new experiments which we believe demonstrate a laser induced collision.

This work was jointly supported by the U.S. Office of Naval Research, the Advanced Research Projects Agency, and the Energy Research and Development Administration.