VELOCITY-AVERAGING EFFECTS ON POLARIZATION MEASUREMENTS IN HOT ATOM REACTIONS

The effects of thermal velocity averaging in polarised 'hot atom' chem ical dynamics experiments have been analysed. Linearly polarised photo lysis of a molecular precursor is assumed to produce anisotropically r ecoiling fragments which collide with target molecules. Analytical exp ressions are deduced which describe the degradation of the degree of a lignment of the collision velocity by the isotropic motions of the pre cursor and target molecules. The efficiencies of different routes to t he solution are discussed. Expressions are given for the overall align ment moments averaged over the distribution of collision speeds, both for the number density of collision pairs and the rate of collisions. The results are illustrated by typical realistic examples. A method is provided for the rapid assessment of the likely significance of these effects in any case of interest.