DYNAMICS OF OZONE PHOTOABSORPTION - A THEORETICAL-STUDY OF THE CHAPPUIS BAND

The first two excited singlet states of ozone are discussed in light of recent ab initio MRD-CI calculations. In the asymmetric pathway for O2 + O fragmentation, the two 1 1A2 and 1 1B1 states undergo an avoided crossing resulting in the C1A" and D1A" states. The D1A" state has bound vibrational levels in the Franck-Condon region while the C1A" is repulsive (towards O2 + O fragmentation) in that area and is found to possess a local minimum away from the Franck-Condon area at small bond angles. A one-dimensional cut along the dissociation reaction coordinate was extracted from the three-dimensional calculated potential surfaces. Quantum mechanical calculations of the absorption spectrum based on these one-dimensional ab initio potentials and of the corresponding ab initio transition moments were undertaken. The present work assigns the distinct features of the Chappuis band to the bound levels of the D1A" state superimposed on the C1A" state continuum as an alternative interpretation of the second absorption band in the ozone spectrum.