Photochemistry of HNCO in Solid Xe: Channels of UV Photolysis and Creation of H2NCO Radicals

Photolysis of HNCO at wavelengths between 266 and 193 nm is studied in solid Xe with FTIR and laser-induced fluorescence methods. The channels HNCO → H + NCO (a) and HNCO → NH + CO (b) are operative in a Xe matrix. Channel b produces both isolated fragments and NH···CO complexes as characterized by the CO absorption. The MP2/6-311++G(3df,3pd) calculations are presented for the NH−CO complexes and compared with the experimental data. Photolysis of NCO produces mainly NO + C. A part of the carbon atoms form C 2 after which C 2 - is created in a photoinduced charge transfer reaction. For comparison, in solid Kr, photolysis of HNCO produces additionally HOCN but this channel is absent in a Xe matrix. Upon annealing of the partially photolyzed matrix at 50 K, hydrogen atoms are mobilized and a radical H 2 NCO is formed by a reaction of a hydrogen atom with a HNCO molecule. Four IR absorptions of H 2 NCO are observed and they agree well with the MP2/6-311++G(3df,3pd) calculations. The assignment is supported by experiments with DNCO. The threshold for the photodecomposition of H 2 NCO is between 365 and 405 nm.