Introduction

For many years two-dimensional (2-D) and three-dimensional (3-D) fragment imaging techniques have been successfully used in the study of molecular structure [1] and for the study of the dynamics of various molecular dissociation processes, such as photodissociation [2], dissociative recombination [3], atom–molecule collision induced dissociation [4], dissociative charge exchange [5], and others (see review by Zajfman and Heber [6]). The basic experimental scheme includes induced dissociation of a single molecule, from either a molecular ion beam or gas target, and the fully correlated measurement of the asymptotic velocity vectors of the outgoing fragments. If the initial velocity of the molecule is large, then all the fragments will be projected into a cone defined by the ratio of their transverse velocities and the initial beam velocity. In such a case, the transverse velocities are deduced from the 2-D position on the surface of a position sensitive detector, while the longitudinal velocities can be derived from the time of arrival at the detector. The specific physical information provided by the images depends on the particular dissociation process. In general, one obtains information about the initial molecular quantum state prior to the dissociation and the final state of the fragments and about the dynamics of the reaction, such as angular dependence, kinetic energy release or potential curves.