Recoil effects of photoelectrons in a solid

TL;DR

This study demonstrates the recoil effect in photoelectron emission from graphite, showing how higher energy photoelectrons cause shifts and broadening in spectra, analogous to the M"ossbauer effect.

Contribution

First direct measurement of recoil effects in solid-state photoelectron spectra across a range of excitation energies.

Findings

Higher excitation energy causes a shift to higher binding energies.

Recoil effects increase with photoelectron energy, affecting spectral shape.

Recoil effects can be modeled similarly to the M"ossbauer effect.

Abstract

High energy resolution C 1$s$ photoelectron spectra of graphite were measured at the excitation energy of 340, 870, 5950 and 7940eV using synchrotron radiation. On increasing the excitation energy, i.e., increasing kinetic energy of the photoelectron, the bulk origin C 1$s$ peak position shifts to higher binding energies. This systematic shift is due to the kinetic energy loss of the high-energy photoelectron by kicking the atom, and is clear evidence of the recoil effect in photoelectron emission. It is also observed that the asymmetric broadening increases for the higher energy photoelectrons. All these recoil effects can be quantified in the same manner as the M\"ossbauer effect for $\gamma$-ray emission from nuclei embedded in crystals.