Determination of the rate constants of the reactions of NO₃ radical with CF₃I and I(²P_3/2)

Abstract

The rate constant of the reaction of NO 3 radical with CF 3 I was determined by a relative rate method using a Fourier transform infrared (FTIR) spectrometer smog chamber with a long path length gas cell. As a result, the upper limit of the rate constant was determined to be <2.2 × 10 −18 cm 3 molecule −1 s −1 in 100 Torr of total pressure at 298 K, which suggests that CF 3 I emitted into the atmosphere accumulates during night. The rate constant of the reaction of NO 3 with I( 2 P 3/2 ) was also measured using time-resolved cavity ring-down spectroscopy. The rate constant showed no pressure dependence in the range of 100-500 Torr of total pressure at 298 K and was determined to be (3.9 ± 1.0) × 10 −11 cm 3 molecule −1 s −1 . The present result is different from the previous ones and is about half of that reported most recently. From this rate constant, it is likely that the reaction of NO 3 radical with I( 2 P 3/2 ) does not have a much influence on the loss of I( 2 P 3/2 ) and the formation cycle of IO radical in the atmosphere. C 2012