The predissociation mechanisms of the e (1)Pi(u) and the b' (1)Sigma(+)(u) states of N-2

A theoretical analysis is given of the photofragment anisotropy of long-lived vibrational states as a function of the rotational level and as a function of the predissociation mechanism. The anisotropy of the lower rotational levels is a strong analytical tool for the identification of the electronic symmetry in the final continuum state. Experiments have been performed on the (4p pi)e (1) Pi(u)(upsilon = 0) Rydberg state and b' 1 Sigma(u)(+) (upsilon = 16) valence state in molecular nitrogen using fast beam translational spectroscopy. The rotational levels of the e (1) Pi(u) state yield both N(S-4) + N(P-2) and N(S-4) + N(D-2) products. We found different angular distributions for S-4 + P-2 and S-4 + D-2 fragments, although originating from the same rotational level. The observed anisotropy parameters, also called beta parameters, have been interpreted and point to the presence of complex predissociation pathways involving mixing with known nearby bound and continuum states. The b' (1) Sigma(u)(+) (upsilon = 16) state produces dominantly S-4 + D-2 fragments. We give a suggestion for the most likely dissociation mechanism based on the observed angular distribution. (C) 1997 American Institute of Physics.