Photochemistry of HNCO in solid xenon: Photoinduced and thermally activated formation of HXeNCO

The preparation and characterization of a novel rare-gas-containing compoun d HXeNCO in solid Xe is described. HXeNCO is formed in two ways. Photolysis of HNCO at 193 nm in solid Xe directly produces HXeNCO providing the first experimental evidence of direct photoinduced formation of a HXY-type rare- gas compound (X = Xe, Kr; Y is an electronegative fragment), which can be a ttributed to relatively high photostability of HXeNCO. This finding particu larly shows that the HXY compounds can be intermediates in the photolysis o f HY in the presence of X. The amount of HXeNCO produced initially in photo lysis of HNCO remains small because HXeNCO decomposes under irradiation. Mo re efficient production of HXeNCO is achieved in the thermal reaction H + X e + NCO --> HXeNCO after photolysis of HNCO. HXeNCO has two strong IR absor ptions: the asymmetric NCO stretch at 2148.3 cm(-1) and the Xe-H stretch at 1788.1 cm(-1). The assignment is supported by the deuteration experiments and the ab initio calculations. HXeNCO decomposes at 405 nm irradiation pro ducing HNCO and (H + NCO).