Some reactions of electronically excited iodine atoms, I(52P½), with halides and oxides

Abstract

Electronically excited iodine atoms in the I(5p⁵²P_½) state, generated by the flash photolysis of CF₃I in the gas phase, have been monitored by kinetic spectroscopy in absorption. The kinetics of the atoms were studied in the presence of a number of halides and oxides where the metathetical abstraction of halogen and oxygen atoms was exothermic and so, on thermochemical grounds, could compete with spin orbit relaxation. In the presence of the allyl halides and of nitrous oxide, the removal of I(5²P_½) was predominantly by collisional quenching, whereas with nitrosyl bromide and chloride, chemical reaction took place. The overall second-order rate constants for the decay of I(5²P_½) in the presence of the gases N₂O, CH₂CH—CH₂Cl, CH₂CH—CH₂Br, CH₂CH—CH₂l NOCI and NOBr were 1.3 × 10^–15, 1.3 × 10^–13, 2.4 × 10^–13, 4.2 × 10^–13, 6.2 × 10^–12 and 9.6 × 10^–12 cm³ molecule^–1 s^–1 respectively, at ∼300 K. Vibrationally excited IO with up to four quanta in the ground electronic state, produced in the photolysis of CF₃I + O₃, results principally from the reaction of O(¹D) with CF₃I rather than that of I(5²P_½) with O₃.