  We report the first direct observation of electron emission into the vacuum
as a result of a VVV Auger transition resulting from the relaxation of a deep
hole in the valence band. A beam of low energy (<1.25eV) positrons was used to
deposit positrons onto the surface of samples consisting of single layer
graphene, multi-layer graphene and graphite. The distribution of electrons
emitted from the samples as a result of the annihilation of the positron showed
peak extending up to ~12 eV with a maximum at ~4eV. The observed peak was ~17
times larger than the previously observed annihilation induced C KVV peak. An
analysis based upon a density functional theory calculation of the positron
annihilation rates indicates that the width and intensity of the peak is
consistent with electron emission resulting from VVV Auger transition excited
by the annihilation of valence band electrons. Good agreement was found between
the data from the single layer graphene on Cu surface with a theoretical line
shape found from a self-folding of the density of states for a free standing
graphene layer. The agreement between the theoretical and measured intensities
for the KVV and VVV transitions indicates that the branching ratio for holes to
decay via an Auger transition is nearly the same in both cases (i.e. close to
100%). Our results suggest the possibility of using annihilation induced VVV
Auger spectroscopy to study the properties of the local density of states and
the hole decay processes in materials in which the valence band width exceeds
the work function.
