Orientation as a probe of photodissociation dynamics

Molecular chlorine was photodissociated in the wavelength range 270È400 nm with 2 linearly polarized light, and the orientation of the excited-state chlorine atom Cl*(2P1@2) was measured by 2] 1 resonance enhanced multiphoton ionization (REMPI) using circularly polarized light. The degree of orientation of the Cl* photofragment is found to oscillate as a function of photolysis wavelength. The oscillation is a result of quantum mechanical coherence arising from electronic states of di†erent symmetry that correlate to the same separated-atom asymptote. A simple curve-crossing model using ab initio potential energy curves reproduces the general shape of the oscillation but fails to give a quantitative Ðt.