Extra-Atomic Relaxation Energies from the Auger Parameter and the Manne-Åberg Sum Rule

Abstract

Core-ionization energies, I, and Auger kinetic energies, K, are affected by both the charge-distribution in the initial state and by relaxation accompanying electron emission. In principle, these can be determined from measurements of the Auger parameter, α = I + K. In the simplest approximation the shift in core-ionization energy, Δ1, between two compounds is given as $$ \Delta = \Delta V - \Delta R $$ (1) where V and R represent, respectively, the contributions from initial- and final-state effects. Because of the cancellation of strictly atomic contributions, ΔR in this case represents the extra-atomic contribution to the relaxation energy. The corresponding expression for the Auger kinetic energy and the Auger parameter, a, are $$ \Delta K = - \Delta V + 3\Delta R $$ (2) $$\Delta \alpha \equiv \Delta I + \Delta K = 2\Delta R $$ (3) The Auger parameter thus provides a direct measurement of the extra-atomic relaxation energy. Combining the Auger parameter with either eq. (1) or (2) gives ΔV, which reflects the initial-state charge distribution. These relationships have, however, been little exploited as a means to determine ΔV and ΔR, perhaps because of uncertainties in the validity of eq. (3).