The effect of light on positron annihilation in natural diamond

The age-momentum correlation (AMOC) technique of positron annihilation spectroscopy has been used to study a gamma-irradiated natural diamond sample. A light-induced reversible change in both the intensity and the lifetime of the trapped positron component in diamond was observed. No signal attributable to positronium was detected in the measurements, supporting the view that positronium formation does not occur in diamond. The measurements demonstrate the sensitivity of positron annihilation to optically active centers in diamond.