Effect of hole-induced shakedown in the Auger spectrum of lanthanum.

Abstract

It is shown from the ${M}_{4}$,5${\mathrm{N}}_{4}$,5X (X=${O}_{1}$,${O}_{2}$,3,${N}_{6}$,7) Auger emissions of La metal, ${\mathrm{La}}_{2}$${\mathrm{O}}_{3}$, and ${\mathrm{LaF}}_{3}$ that the 4f hole pulled down below the Fermi level by the 3d core hole in La metal is significantly populated before Auger decays take place. This extra relaxation mechanism by the ${N}_{4}$,5VV Auger process from conduction electrons gives important contribution to the intensity of the ${M}_{4}$,5${\mathrm{N}}_{4}$,5${\mathrm{N}}_{6}$,7 Auger emission. The amount of this contribution can be calculated by existing theories on the shakeup or shakedown satellites on the La 3d core-level x-ray photoemission spectra (XPS) of these La compounds, and the results are found to be consistent with our experimental data. The criterion for the importance of this hole-induced shakedown process in the initial state of Auger spectra is determined, and the implications of this finding on other spectroscopies are discussed.