The axial recoil approximation holds that when a diatomic molecular ion is formed in a dissociative state, the atoms produced in the dissociation 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 approximation 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 translational velocities of the target molecules, and for instrumental effects. In the analysis of the N 2 data, the corrections have the effect of smoothing the predicted angular distribution functions. The amount of the smoothing depends primarily on the temperature of the target gas and the shape of the potential-energy curve for the N 2 2ϩ final state involved in the Auger transition.

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400 eV electrons were used to excite the autoionizing state Q 1 1 + g of H 2 . The relative cross section was measured as a function of: (1) the angle between the internuclear axis and the momentum transfer vector of the collision; and (2) energy loss for a fixed orientation of the molecular axis in the laboratory frame. In the first set of measurements electrons scattered at 18 • with an energy loss of 29 eV were detected in coincidence with a 2 eV H + ion resulting from dissociation following autoionization. The angular distribution of the 2 eV ions was recorded and fitted to calculated values. A maximum was found when the internuclear axis was aligned with the momentum transfer vector. Secondly, the relative yield of 2 eV H + ions was measured as a function of energy loss in the electron-H 2 collisions. Energy loss ranged from 23 to 35 eV. The lowest lying Q 1 1 + g , 1 + u and 1 g were included in the calculated fit to the data.

Procedures for calculating the angular distribution of Auger electrons emitted by homonuclear diatomic molecules are presented. The calculation is performed in prolate spheroidal coordinates. A two-center effective potential is introduced to simplify the Schrodinger equation for an electron moving under the inhuence of the nuclei and other electrons. The effective potential is expressed by having equal Axed effective charges on each nucleus. The wave functions for the bound-state molecular orbitals and those for the Auger electron are obtained by solving the Schrodinger equation in which the appropriate experimental energies are used as the eigenvalues. The transition moments and the angular distribution of the Auger electron in the molecular frame are obtained by numerical integrations. For a specific Auger transition process, the distribution function is expressed in terms of the absolute square of a coherent sum of prolate spheroidal functions. In order to compare the predicted distribution function to our experimental results, corrections due to the rotation of the molecular ions during the course of dissociation are made.PACS number(s): 33.80.Eh