State-selective photochemistry: Energy distribution in the no fragment a photodissociation of the CH 3ONO nπ* state

Abstract

The vibrational and rotational state distributions of the NO X 2Π fragment resulting from photodissociation of cis-CH 3ONO excited in specific NO stretching vibrational levels of the neπ* state at 364, 350, 338, 328 and 318 nm have been determined. The NO X ν″ = 0, 1, 2, 3, 4 probed by two-photon laser-induced fluorescence exhibits a large amount of rotational excitation which is independent of the excitation wavelength. The NO X vibrational population varies with the vibrational level prepared in the parent excited molecule and the results show that the excess vibrational energy deposited in the N0 stretching mode of the CH 3ONO nπ* state is retained in the vibration of the free NO fragment. The rotational excitation is interpreted in terms of interfragment ccupling due to the impulse applied to the recoiling fragments. The vibrational distribution is more likely to be explained by a simple model based on intrafragment coupling which takes into account the change in N0 bond length between the ground and dissociative state of the molecule.