Formation and characterization of neutral krypton and xenon hydrides in low-temperature matrices

A family of rare-gas-containing hydrides HXY (where X=Kr or Xe, and Y is an electronegative fragment) is described. These molecules are experimentally prepared in low-temperature matrices by photodissociation of a hydrogen-containing HY precursor and thermal mobilization of the photodetached hydrogen atoms. The neutral HXY molecules are formed in a concerted reaction H+Y --> HXY. Experimental evidence for the formation of these species is essentially based on strong infrared absorption bands that appear after annealing of the photolyzed matrices and are assigned to the H-X stretch of the HXY molecules. Computationally, the formation of these HXY molecules decreases the H-X distance by a factor of greater than or equal to2 from its van der Waals value, which emphasizes their true chemical bonding, possessing both covalent and ionic contributions. The estimated dissociation energies vary from 0.4 to 1.4 eV and hold promise for forthcoming observation of these molecules in the gas phase. The experiments with the HXY molecules widen our knowledge on solid-state photolysis dynamics of hydrogen-containing species. In particular, the photolysis of small HY hydrides in solid Xe seems to be a quite local process, and the accompanying losses of H atoms play a minor role. (C) 2000 American Institute of Physics. [S1063-777X(00)00909-9].