Photolabile xenon hydrides: A case study of HXeSH and HXeH

The photo-induced transformations of HXeSH and HXeH under the action of IR and visible light have been studied using FTIR spectroscopy. The xenon hydrides were produced by the X-ray induced decomposition of H2S and its isotopomers in a solid xenon matrix at 7.5 K followed by thermal annealing at the temperatures up to 45 K. Selective IR-induced photodissociation of HXeSH at 3500–2500 cm−1 was attributed to vibrational excitation of the 3νH–Xe mode. The IR-photodecomposed HXeSH molecules can be almost quantitative recovered below 22 K with very small effective activation energy (∼20 meV) indicating local character of this process. Analysis of the photoactivity of xenon hydrides in the visible region revealed previously unknown absorptions for HXeSH (in the region of 400–700 nm) and HXeH (above 700 nm). The decomposition of HXeH occurs due to both direct photolysis and reactions of “hot” H atoms produced from the photodissociation of HXeSH. The efficiency of thermal recovery for both xenon hydrides after photolysis with visible light was found to be dependent on the excitation wavelength, which was explained by the effect of photon energy on spatial distribution of the dissociation fragments.