Photodissociation dynamics of HNO 3 at 266 nm

Abstract

The photodissociation dynamics of HNO 3 at 266 nm has been investigated by measuring laser induced fluorescence spectra of the OH( 2п) fragments. The measured fractions of the available energy distributed among the fragements are ƒ t = 0.21, ƒ r ( OH) = 0.047 , ƒ int ( NO 2) = 0.74 , and negligible OH fragments are found in the vibrationally excited states. By analyzing Doppler profiles of the spectra, vector correlations in the photodissociation of HNO 3 have been measured. The measured correlations show that the transition is parallel ( β μv = 1.0) but the transition dipole moment and the recoil velocity of the fragment are not exactly parallel. The rotational angular momentum J of the product OH is aligned parallel to the recoil direction of the fragment. From the measured correlations and the large fraction of the internal energy in the NO 2 fragments, it has been concluded that the transition at 266 nm is described as vibronic to the pyramidal excited state of A″ symmetry. Together with the measured Λ-doublet distribution of the OH fragments, the dynamics of photodissociation is discussed in detail.