Alignment measurements in orbitally selective collision-induced fluorescence

Abstract

The results of an experiment in which the polarization of collisionally redistributed near-resonant light was monitored have been analysed. If the incident light is polarized the fluorescent light may also be, with its degree of polarization depending on the collision dynamics. The experimental results have been analysed using a model in which the collision complex is treated as a transient quasi-molecule. In this model the atom–perturber complex is excited directly into a molecular orbital which rotates through the collision. The complex then decouples and the atom radiates at a later time. The rotation experienced during the collision accounts for the depolarization of the light. A knowledge of the interatomic potentials for the system under study is necessary for a quantitative application of the theory. The 2537 A(3P1–1S0) line in Hg perturbed by Kr was chosen for the present work since the interatomic potentials for this system are well documented. It is shown that the primitive from of the decoupling radius model is inadequate to account for the experimental results quantitatively. Extensions and modifications to the model that overcome some of these difficulties are discussed. The results highlight the poor orbital selectivity attainable in this type of experiment when the molecular potentials do not separate sufficiently rapidly as the collision partners approach one another.