Photochemistry of hydrogen peroxide in Kr and Xe matrixes

UV photolysis of hydrogen peroxide (H2O2) in various rare-gas matrixes is c omparatively studied. The photorecovery of H2O2 from the tight H2O ... O co mplex is observed in Kr and Xe matrixes, in addition to this reaction in an Ar matrix found previously. The similarity of spectral position and effici ency of the photorecovery reaction in various rare-gas solids indicates its fundamental character, supports charge-transfer excitation of H2O ... O as its origin, and preserves promises to find this photoreaction in media of environmental importance. In UV photolysis of H2O2, the relatively small co ncentration of isolated OH radicals is found in a Kr matrix, and no OH radi cals appear in a Xe matrix, and this trend is discussed in terms of delayed cage exit. Moreover, additional species photogenerated from H2O2 in a Xe m atrix as well as the absence of OH radicals might be connected with partici pation of some hidden intermediates (HOXeOH, HXeOOH, etc.) in the dynamics, thus, catalyzing new photodissociation channels. Among the photolysis prod ucts, the loose H2O//O complex is suggested to be stabilized in Kr and Xe m atrixes. This loosely bound complex is quasistable and decomposes at relati vely low temperatures (below 20 K) quantitatively forming the known tight H 2O ... O structure. This low-temperature process offers one additional exam ple of short-range atomic mobility introduced recently in the literature. ( C) 2000 American Institute of Physics. [S0021-9606(00)00605-X].