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Time-resolved spectroscopic techniques are used to examine the photochemistry of OClO in water, alcohol, acetonitrile, toluene, and sulfuric acid solutions. In all solvents, excitation of the near-UV ,A2 -,BI transition leads to two competing photochemical reactions: dissociation into OC1 + 0 and formation of C1 + 0 2 .Based on orbital correlations of the isolated molecule, C1 can be formed by two distinct mechanisms, (1) direct elimination of C1 from OC10, maintianing the GV symmetry axis along the reaction coordinate to form C1+ 02('Ag), and (2) isomerization to C100, which thermally dissociates into C1+ 0 2 . Experimental evidence supporting both pathways for the condensed phase reactivity of OClO is presented. The quantum yield for direct elimination of C1 is solvent dependent. The role of ClOO in the excited state photochemistry of OClO is discussed in detail. In many of the solvents studied, a photogenerated transient forms within the instrument response that absorbs in the blue-green region of the optical spectrum. This species reveals identical kinetics to those exhibited by the UV absorption assigned to C100. These observations provide compelling evidence that ClOO has electronic excited state(s) similar in energy to the lowest energy states of OC10. The potential involvement of low-lying electronic states of ClOO in the photochemistry of OClO is discussed.

Polarizability response spectroscopy, a two-color optical Kerr effect method, has been developed and employed to study solvent intermolecular polarizability responses to photoexcited solutes. Here, we report solvent intermolecular polarizability responses in ͑dipolar͒ solvation. The time-resolved nonresonant polarizability signals are analyzed in the frequency domain where they are fit to a functional form representing diffusive reorientational, interaction-induced, and librational motions. Diffusive reorientational motion of CHCl 3 was preferentially driven following photoexcitation of Coumarin 153 while interaction-induced motion was mainly driven in CH 3 CN solutions. The mechanism for selective solvent responses involves the relative orientation of the solvent dipole and most polarizable molecular axes and their interaction strength to the solute dipole.