PHOTODISSOCIATION DYNAMICS OF HNO3 AT 266 NM

The photodissociation dynamics of HNO3 at 266 nm has been investigated by measuring laser induced fluorescence spectra of the OH((2) Pi) fra gments. The measured fractions of the available energy distributed amo ng the fragments are f(1) = 0.21, f(r)(OH) = 0.047, f(int)(NO2) = 0.74 , and negligible OH fragments are found in the vibrationally excited s tates. By analysing Doppler profiles of the spectra, vector correlatio ns in the photodissociation of HNO3 have been measured. The measured c orrelations show that the transition is parallel (beta(mu v) = 1.0) bu t the transmission dipole moment and the recoil velocity of the fragme nt 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 interna l energy in the NO2 fragments, it has been concluded that the transiti on at 266 nm is described as vibronic to the pyramidal excited state o f A('') symmetry. Together with the measured Lambda-doublet distributi on of the OH fragments, the dynamics of photodissociation is discussed in detail. (C) 1997 Elsevier Science S.A.