Ion-Neutralization Spectroscopy of Nickel

Abstract

The neutralization of ions of large neutralization energy such as He⁺ ejects electrons from solids in a two‐electron, Auger‐type process which extends to electrons quite deep in the band. The kinetic energy distribution of such electrons can be unfolded to give a function U (ζ) of band energy ζ called the transition density, which contains factors dependent on electronic state density in the solid and transition probability of the process. The method is a spectroscopy of solids (INS) which probes the local density of states in the surface region. The U (ζ) function for Ni shows a peak just below the Fermi level whose width agrees quite well with Mueller's theoretical result. It is possible that INS sees a somewhat narrower d band than other methods because the ion interacts principally with surface atoms, which have a weaker interaction with fewer neighbors than do bulk atoms. Ion‐neutralization spectroscopy is also very sensitive to the presence of foreign atoms such as oxygen, and has been used to observe the virtual states of electrons in such atoms adsorbed in ordered monolayers on the solid surface.