PHOTODISSOCIATION OF OZONE IN THE CHAPPUIS BAND .2. TIME-DEPENDENT WAVE-PACKET CALCULATIONS AND INTERPRETATION OF DIFFUSE VIBRATIONAL-STRUCTURES

We present time-dependent wave-packet calculations describing the phot odissociation of ozone in the Chappuis band, which evolves in the two lowest states of (1)A '' symmetry. The calculations are performed in t he diabatic representation and include the coupling between the two re levant states. All three nuclear degrees of freedom are taken into acc ount. The two potentiaI-energy surfaces, the coupling potential, and t he two transition-dipole-moment functions with the electronic ground s tate have been calculated previously by ab initio methods [Woywod er n l., J. Chem. Phys. 107, 7282 (1997)]. The coupling between the two dia batic states is exceedingly strong, resulting in very fast dissociatio n into O+O-2 on the time scale of only one symmetric stretch period. A small portion of the initially created wave packet is temporarily tra pped leading to three tiny recurrences, which reflect basically symmet ric stretch motion plus same amount of bending motion. The experimenta lly observed diffuse vibrational structures superimposed to the broad absorption spectrum are satisfactorily reproduced and discussed both i n the time-independent and the time-dependent picture of spectroscopy. In view of the very short lifetime in the excited states, the corresp ondingly large widths of the diffuse structures, and the participation of all three vibrational modes we conclude that an unique assignment in terms of three quantum numbers is not possible. The main structures are due to symmetric stretch excitation, but bending and even asymmet ric stretch motion are also involved. A one-state model, in which only the upper (bound) adiabatic potential is employed, provides a qualita tively correct explanation of the absorption spectrum and the diffuse structures. (C) 1997 American Institute of Physics.