Photodissociation dynamics of the charge-transfer state of the C6H6-I-2 complex

A pulsed-extraction time-of-flight method was employed to investigate the photodissociation dynamics of the C6H6-I-2 charge-transfer state. Measurement of the kinetic energy release for the I atom fragments indicates that the charge-transfer state dissociates to a I(P-2(3/2)) + I*(P-2(1/2)) product state. An anisotropic high-velocity distribution and a Maxwell-Boltzmann distribution with a velocity-dependent spatial anisotropy were observed as distinct components in the product spectra. Rapid dissociation from an oblique complex geometry, with the I-2 bond axis inclined at an angle with respect to the benzene symmetry axis, appears to be responsible for the experimental results. The free I atom recoils away from the complex while the bound I atom interacts strongly with the benzene partner, yielding the different fragment distributions. As a result of charge-transfer excitation, the I-2 is left On the same repulsive excited state that is optically accessed in the uncomplexed molecule, leading to prompt fragmentation. A second mechanism, producing slow I atom fragments, may also contribute to the Maxwell-Boltzmann component. The C6H6-I-2 complex manifests behavior that can only be understood on the basis of the entire supramolecular complex while other aspects can be rationalized from characteristics of the separated fragments.