Recoil effects of photoelectrons in a solid

Abstract

High-energy-resolution $\mathrm{C}\phantom{\rule{0.2em}{0ex}}1s$ photoelectron spectra of graphite were measured at excitation energies of 340, 870, 5950, and $7940\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ using synchrotron radiation. On increasing the excitation energy, i.e., increasing kinetic energy of the photoelectron, the bulk origin $\mathrm{C}\phantom{\rule{0.2em}{0ex}}1s$ 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 $\ensuremath{\gamma}$-ray emission from nuclei embedded in crystals.