Time-resolved FTIR emission study of product dynamics in the NO+NCO reaction

Abstract

Product IR chemiluminescence in the NO+NCO reaction has been recorded using time-resolved FTIR spectroscopy. Emission was observed from highly vibrationally excited CO ₂ and N ₂ O, produced from two competing channels and emitting in the Δv ₃ =-1 transitions between 2000–2400 cm ^-1 . The spectra are consistent with both molecules having total vibrational energies which are approximately equal to those predicted from prior distributions, but the partitioning between the individual vibrational modes is markedly non-statistical. In particular, CO ₂ exhibits much less excitation in ν ₃ (estimated as 0.6±0.2 quanta per molecule) than statistically predicted. Emission from the (0, 0, 1) levels of both CO ₂ and N ₂ O was measured, and their relative intensities and kinetic behaviour shown to be consistent with a model of relaxation of the nascent vibrational distributions in which product-channel branching ratios were taken to be equal to those previously determined from end-product analyses.