Product state distributions in the photodissociation of expansion-cooled NO 2 near the NO(X 2Π) ν=1 threshold

Abstract

The photodissociation of NO 2 near the NO ν=1 threshold was studied using a supersonic molecular beam of NO 2 and multiphoton ionization detection of NO(X 2Π 1 2 , 3 2 ). The vibrational populations near the ν=1 threshold are nonstatistical as compared with the predictions of phase space theory (PST). The rotational distributions in both NO ν=0 and 1 show pronounced structures and fluctuations; however, their average is described fairly well by PST, suggesting that the decomposition of NO 2 at λ ⩾ 370 nm can be viewed as vibrational predissociation on the mixed X 2A 1/1 2B 2 surface. Similar structured rotational distributions have been observed by Miller et al. in recent studies of the photodissociation of CO 2 at 157 nm. The structures in the rotational distributions are interpreted as fluctuations inherent in the decomposition of an excited complex with many overlapping resonances (Ericson fluctuations).