H atom mobilies in xenon matrices. Dependence on matrix morphology

The concentration of H atoms in xenon matrices, produced by 193 nm photolysis of HBr, has been monitored by laser-induced emission from xenon—hydrogen exciplexes. At 10 K the H-atom concentration remains unchanged over the course of five days. At 40 K the majority of atom loss occurs on a timescale of minutes and is sensitive to matrix preparation. At 40 K diffusion coefficients for the major H atom loss processes have been estimated as 5.0×10 −14 cm 2 /s and 2.6×10 −13 cm 2 /s for xenon matrices deposited at 28 and 10 K respectively. An upper limit of ≈ 10 −17 cm 2 /s can be obtained for the diffusion coefficient at 10 K. The effect of matrix morphology on atom mobilities is discussed.