Effect of recoil-induced internal excitation on the Auger transition energy

Abstract

A recent investigation of nitrogen $1s$ ionization in ${\mathrm{N}}_{2}$ by 40-keV photons has shown that only 70% of the recoil-induced internal energy appears as kinetic energy of the two nitrogen ions that are produced following the Auger decay of the core-ionized molecule. It has been concluded that the remaining 30% appears as part of the Auger transition energy. Presented here is an investigation using both classical and quantum mechanical models of how this unexpected result might come about. With these models, and the assumption of an isotropic distribution of the recoil momentum with respect to the molecular axis, it is possible to account for as much as 16% of the internal excitation contributing to the Auger transition energy, but within this framework there does not seem to be an obvious mechanism for producing a contribution as high as 30%. Consideration of refinements to the simple models does not improve this disagreement between prediction and observation. Assumption of a sufficiently anisotropic angular distribution can bring prediction and experiment into agreement, but such anisotropy is not consistent with other experimental results or theoretical expectations.