Vibrational relaxation of NO(nu=1-3) and NO2(0,0,1) with atmospheric gases

Measurements are reported of the vibrational quenching of NO(v = 1-3) by NO 2 and O-2, and of NO2(0,0,1) by NO, O-2 and N-2, close to room temperature. Vibrationally excited NO was formed from the photolysis of NO2 at 308 and 355 nm, and the kinetic behaviour of the different levels was followed by w avelength resolved FTIR emission. The rate constant for the removal of NO(v = 1) by NO2, (1.9 +/- 0.2) x 10(-12) cm(3) molecule(-1) s(-1), is in excel lent agreement with previous measurements. For v = 2 and 3 the rate constan ts showed a marked increase, with values of (2.9 +/- 0.3) and (4.8 +/- 0.7) x 10(-12) cm(3) molecule(-1) s(-1) respectively, and the relaxation proces s was found to proceed dominantly through single quantum transitions in NO. However, simultaneous observation of emission from the (0,0,1) level of NO 2 revealed that although single quantum exchange between NO and NO2(0,0,1) is close to resonance it took place with less than 50% quantum efficiency. The results are discussed in terms of formation of a N2O3 complex in which free flow of energy is incomplete. For quenching by O-2, energy transfer ag ain was found to be dominated by single quantum loss in NO, with rate const ants of (2.4 +/- 0.2), (5.3 +/- 2.6) and (12 +/- 4) x 10(-14) cm(3) molecul e(-1) s(-1) for v = 1, 2 and 3, respectively, in good agreement with previo usly reported values. Vibrationally excited NO2 was produced by the reactio n of NO with NO3, and its quenching kinetics studied by observation of time resolved emission. Rate constants were found to be (4.0(-1.5)(+1.9)) x 10( -12), (1.8(-0.8)(+1.1)) x 10(-13) and (3.1(-1.0)(+1.3)) x 10(-14) cm(3) mol ecule(-1) s(-1) for quenching by NO, O-2 and N-2 respectively. The results show that for the first two species the rate constants are similar to those previously reported for quenching of NO2 with moderate but unspecified exc itation in the v(1) and v(3) modes, but for N-2 the present value is a fact or of four lower. As quenching rate constants for the v(1) + v(3) modes hav e been used for estimations of the atmospheric quenching rate of NO2(0,0,1) , the present results suggest that these estimates need downward revision b y approximately a factor of 2.5.