Low-temperature photolysis of hydrocarbons in solid xenon: Evidence for metastable XenH

Abstract Xe crystals, doped with hydrogen-containing compounds in ppm concentrations, show strong dose-dependent absorption bands between 6.2 and 6.9 eV after irradiation with X-rays or UV light. We show, by chemical and isotopic doping experiments, that the origin of these bands is a “caged” H atom, or a thermally unstable Xe n H molecule, with a binding energy of a few meV. The generation and decay dynamics are modelled, and the vibrational energies in the ground and first excited states are deduced to be ⪢ 29 and 102 meV, respectively.