PHOTOINDUCED CHARGE-TRANSFER DISSOCIATION IN VANDERWAALS COMPLEXES .2. NA2...CICH3, NA2...(CICH3)2, AND NA...FPH

van der Waals complexes Na(m)...(XR)n (R = CH3 and Ph; X = Cl and F) have been generated by crossing a beam of Na with a supersonic jet of halide molecules XR seeded with Ar. The complexes were identified and measured by photoionization time-of-flight mass spectrometry. Tunable visible radiation (530-680 nm) was used to measure the photodissociation spectrum (an ''action spectrum'') of these clusters. The peak cross section for photodissociation of Na2...(ClCH3)n (n = 1 and 2) was found to be large (approximately 6 angstrom2) with its maximum at 635 nm for n = 1 and at 615 nm for n = 2. These peak wavelengths suggest that the primary route for photodissociation is excitation of the Na(m) followed by charge-transfer dissociation: Na2...(ClCH3)1,2 + hv --> [Na2*...(ClCH3)1,2]double dagger --> [Na2+..(ClCH3)1,2-]double dagger --> products (the double dagger indicates a,transition state). By contrast, the photodissociation of Na2+... (ClCH3) appeared to follow a direct mechanism involving the dissociation of the [Na-Na]+. For Na...FPh, two excited states of-the complex (PI and SIGMA) were thought to be responsible for the two broad peaks in the action spectrum, each with vibrational structure.