SPECTATOR AND PARTICIPATOR AUGER TRANSITIONS BY RESONANT EXCITATION OF THE MO 2P(3/2) ORBITAL IN LI2MOO4, MOO3, AND MOS2

The Auger decay process after resonant Mo 2p3/24d(5s) excitation in the molybdenum compounds has been studied by photoemission spectroscopy using synchrotron radiation. It was found that the Mo(L3M4,5M4,5) Auger lines are split into double-peak structures (Li2MoO4 and MoO3) or broadened (MoS2) at the resonant photon energy. These results are attributed to spectator Auger and normal Auger transitions. The spectator Auger lines were found to shift to the higher kinetic energy by 4.512 eV. Amount of the energy dispersions and direction of the shifts, almost in proportion to the photon energy, are interpreted in connection with bandlike structure of the unoccupied molecular orbitals in solids compared to isolated atoms or free molecules in a gas phase. The resonantly excited state was also found to decay through the direct recombination between the excited electron and core hole, leading to emission of an electron from one of the outer orbitals. This type of transition, called a participator Auger transition, was especially enhanced in the decay involving the Mo 3d3/2,5/2 orbitals with drastic change in the photoemission branching ratio of 3d5/2 to 3d3/2. © 1994 The American Physical Society.