Effect of temperature on positronium annihilation in silica gel.

A systematic temperature-dependent study of positronium annihilation rate within the void spaces (micro- and mesopores) of silica gel material has been performed through positronium annihilation spectroscopy. The results find their plausible interpretation through a novel theoretical explanation based on vibrational interaction of thermally energized atoms on the surface layer of the pores with positronium, which in fact justifies the observed increase in the annihilation rate of the latter, with the increase in temperature.