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-co ntaining HY precursor and thermal mobilization of the photodetached hydroge n atoms. The neutral HXY molecules are formed in a concerted reaction H+Y - -> HXY. Experimental evidence for the formation of these species is essenti ally 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 m olecules. Computationally, the formation of these HXY molecules decreases t he H-X distance by a factor of greater than or equal to2 from its van der W aals value, which emphasizes their true chemical bonding, possessing both c ovalent and ionic contributions. The estimated dissociation energies vary f rom 0.4 to 1.4 eV and hold promise for forthcoming observation of these mol ecules in the gas phase. The experiments with the HXY molecules widen our k nowledge 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].