Nitric oxide chemiexcitation occurring in the reaction between metastable nitrogen atoms and oxygen molecules

The infrared emission spectrum of the NO Δv=1 bands, chemiexcited in the reaction between metastable atomic nitrogen and molecular oxygen, has been studied at temperatures of 90–180 K and pressures near 5×10−6 atm. It is concluded that the observed radiation corresponds to an NO vibrational distribution created solely by the chemical reaction, unaffected by any relaxation process(es). Relative rate constants for production of NO into individual vibrational levels are found to be very nearly constant for levels v=1–7 and decrease monotonically for levels v=8–12. The average degree of excitation is about 4.5 vibrational quanta per NO molecule, and, assuming that N(2P) atoms play a negligible role, it is determined that 27% of the N(2D)+O2 exothermicity is converted to vibrational excitation of the nitric oxide product. Both the nature of the distribution and the results of a surprisal analysis suggest that those reactions which produce NO in levels higher than v=7 may also be producing O(1D).