Table of Contents
Laser Chemistry
Volume 11, Issue 3-4, Pages 177-186
http://dx.doi.org/10.1155/LC.11.177

High Resolution Laser Techniques Applied to Reaction Dynamics

Laboratoire Aimé Cotton. C.N.R.S. II., Orsay Cedex 91405, France

Copyright © 1991 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The applications of high resolution laser techniques to crossed-beam experiments which are examined in this paper concern: (a) the reactivity of atomic/molecular excited states and the influence of light polarization and (b) the measurement of absolute and differential cross sections by use of the laserinduced fluorescence technique performed in a coherent saturation regime.

Examples are provided by the crossed-beam study of the Cs(7P) + H2CsH + H photochemical reaction, where two C.W. single-mode tunable lasers are used to excite Cs atoms and to probe CsH product molecules. It is shown how the fine and hyperfine structures of the Cs atom are involved in the reaction mechanism (harpooning). The measurement of the total cross section (≈4.10−16cm2) gives an indication of the overall efficiency of the reactive process (Cs atoms in the 7P state) with respect to the quenching ones (Cs atoms in 6S, 6P, 5D and 7S states). Finally, the differential cross section shows a marked forward “peaking” of CsH products which narrows with collision energy but which is rather independent of the product rotation.