FEATURE STATE ASSIGNMENT AND HIERARCHICAL AND STATISTICAL-ANALYSES OF VIBRONIC AND ROVIBRONIC LEVEL STRUCTURE OF NO2 IN THE 16300-25130-CM(-1) REGION

The laser induced fluorescence (LIF) spectrum of jet-cooled NO2 in the energy range from 16 300 cm(-1) up to the dissociation limit at 25 130.6 cm(-1) was measured with an energy resolution of 0.4 cm(-1), and vibronic interaction was discussed through a feature state assignment and a hierarchical analysis. By convoluting the spectrum, the feature states representing bending excited levels in the B-2(2) state were identified. The hierarchical level structure just below the dissociation limit was interpreted in terms of a stepwise intramolecular vibronic energy redistribution (IVR) caused by the anharmonic couplings within the B-2(2) state followed by the vibronic and rovibronic couplings between the B-2(2) and (2)A(1) states. In a higher resolution (similar to 0.04 cm(-1)) measurement the transitions to the rovibronic eigenstates just (0-55 cm(-1)) below the dissociation limit were resolved. The observed vibronic level density having b(2) symmetry, rho(vib)(b(2))=1.6/cm(-1), in this energy region is derived from the observed peak density, rho(peak)=9.6/cm(-1), by assuming a strong K mixing. The observed large peak density was ascribed to the large anharmonisity of the ground state potential energy surface near the dissociation limit. The statistical analyses applied to this eigenstate spectrum Showed an extremely strong correlation among these eigenstates, indicating the complete IVR. The present results of the statistical analyses near the dissociation limit support the statistical behavior in the dissociation dynamics just above the dissociation limit investigated in our previous paper [J: Chem. Phys. 99, 254 (1993)].