LIMITATIONS OF THE AXIAL RECOIL APPROXIMATION IN MEASUREMENTS OF MOLECULAR DISSOCIATION

The axial recoil approximation holds that when a diatomic molecular io n is formed in a dissociative state, the atoms produced in the dissoci ation process will move outward along the straight line defined by the internuclear axis of the molecule. Analysis of experiments measuring the angular distribution of Auger electrons emitted by N-2 following K -shell ionization of N-2 molecules shows that the axial recoil approxi mation is not strictly true. Significant corrections must be made for the rotation of the molecule during the time of dissociation. Smaller corrections must be made for the thermal distribution of the translati onal velocities of the target molecules, and for instrumental effects. In the analysis of the N-2 data, the corrections have the effect of s moothing the predicted angular distribution functions. The amount of t he smoothing depends primarily on the temperature of the target gas an d the shape of the potential-energy curve for the N-2(2+) final state involved in the Auger transition. (C) 1997 American Institute of Physi cs.