A MODEL FOR NONADIABATIC COUPLING IN THE PHOTODISSOCIATION OF I-2-SOLVENT COMPLEXES

Experiments performed on moderately dense gases indicate that the absorption of photons with energies in excess of the dissociation energy of I2 often fails to cause dissociation and, instead, results in the direct production of iodine molecules in the ground electronic state. To account for this, Otto, Schroeder, and Troe (OST) proposed that the photons are absorbed by I2-solvent complexes from which the solvent subsequently is ejected and the 12 simultaneously deposited in the electronic ground state. Our earlier calculations (for solvent ethane) already have established that the concentrations Of I2-Solvent complexes are, indeed, large enough to satisfy the requirements of the OST model. What we now propose is a dynamic mechanism that accounts for the photoabsorptive dissociation of the complex into a solvent fragment and a vibrationally excited 12 molecule in the ground electronic state. The occurrence of such an event is surprising because, at first glance, it appears to violate commonly accepted notions about the interconversion of electronic and nuclear, kinetic energy.