A RESONANCE RAMAN POLARIZATION STUDY OF THE MODE-SPECIFIC SUBPICOSECOND PHOTODISSOCIATION OF THE NO2 2B-2(2) STATE

Vibronically specific subrotational period lifetimes of the predissoci ated 2B-2(2) state of NO2 vapour (250-235 nm) have been determined by spontaneous resonance Raman scattering polarization measurements. The lifetimes of the vibronic symmetric stretching, nu1', (100), bending, nu2', (101), and asymmetric stretching, nu3', (002), overtone levels a re 75 +/- 10 fs, 2.5 +/- 0.5 ps and 155 +/- 15 fs respectively. When o ne quantum of bending (nu2') is excited in combination with one quantu m of totally symmetric stretching (nu1'), the lifetime increases from 75 +/- 10 to 125 +/- 15 fs (110). The 2B-2(2) state electronic origin lifetime has been previously shown to be 42 +/- 5 ps independent of an gular momentum quantum numbers. These results are interpreted in terms of the shape of the potential energy surface intersections in the reg ion and the results of earlier quantum yield measurements.