MATRIX-ISOLATION FOURIER-TRANSFORM INFRARED AND AB-INITIO STUDIES OF THE 193-NM-INDUCED PHOTODECOMPOSITION OF FORMAMIDE

Ultraviolet irradiation of formamide in solid argon forms hydrogen-bon ded, carbon- and oxygen-attached complexes NH3-CO and NH3-OC. Computat ionally, the carbon-attached complex is 1.2 kJ mol(-1) more stable tha n the oxygen-attached complex. However, a thermal equilibrium of the t wo structures is found experimentally in the matrices. Moreover, the o xygen-attached complex dominates in the 193-nm-induced photolytic comp lex formation from formamide. In xenon matrices, the photochemistry of formamide increasingly yield the HNCO+H-2 binary system. The change i n photochemistry of formamide between the argon and xenon enviroments can be attributed to an external heavy-atom effect, where xenon enhanc es the rate of intersystem crossing from a singlet to a triplet surfac e.