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Imaging techniques for the study of chemical reaction dynamics.

In recent years the development of new techniques to study gas-phase reaction dynamics of full and half collisions has been tremendous. The ultimate goal in this field of research is to achieve control of chemical reactions. Levine & Bernstein ( 1) have outlined desiderata for the study of molecular reaction dynamics, stating that in the ultimate experiment one would like to determine the total cross section at specified collision energies; measure the internal-state, angular and velocity distributions, and alignment of the products; and prepare selectively the internal state, alignment, and orientation of the reactants. So far no experiment has simultaneously implemented all of these desiderata. Levine & Bernstein considered many experiments in which determination of a few of the desiderata has been achieved simultaneously. Considerable advances have been made since their review. Some of these are highlighted in this review. The majority of studies of chemical reactions focus on the asymptotic properties of the reaction, measuring the quantum-state or velocity (speed and angle) distributions of the products. Newly developed techniques for the simultaneous measurement of these properties are the subject of this review. Simultaneous measurement is important so that correlated quan­ tities (e.g. the quantum state of one product correlated with that of the other or the velocities of fragments correlated with the particular quantum