Energy distributions and excitation probability of nickel atoms sputtered from Ni3Al, NiAl and Ni

The resonant electron tunnelling (RET) model for the sputtering of atoms in excited electronic states has been tested for Ni atoms sputtered from Ni, Ni3Al and NiAl. Laser sputter neutral mass spectrometry using one-colour two-photon ionisation schemes has been used to measure the relative yields of atoms sputtered into the 3F ground atomic state and the 3D metastable state. It is found that more Ni atoms are sputtered into the excited state than the ground state, and that the energy distribution of sputtered atoms peaks at a higher energy for the excited state compared to the ground state, as found previously. In addition the relative population of the 3D state is more pronounced for NiAl than for Ni3Al or Ni. This is due to the increased interaction strength in NiAl, due to greater overlapping between the surface and atomic electronic structures.