Photodissociation of chlorine isocyanate

Gaseous ClNCO exhibits a continuous ultraviolet absorption feature peaked near 250 nm. Photolysis of this compound at 249 nm produces bright blue emission identified as the A 2Σ+→X 2Π transition in NCO. The excited NCO arises from a collisional process in which N(2D) atoms, produced directly by the photodissociation, react with the parent ClNCO. The rate constant for this process is k=(2.1±0.2)×10−11 cm3 s−1. From production of N(2D) by the 249 nm photolysis, the heat of formation of gaseous ClNCO is inferred to be ΔHf(ClNCO)≥52.9 kcal mol−1. ClNCO is metastable with respect to the ground electronic states of NCl and CO by 8.2 kcal mol−1.