Photodissociation of carbon cluster cations.

Mass resolved carbon cluster cations from C sub 3 sup + to C sub 20 sup + have been photofragmented using 248 nm and 351 nm light. For an initial cluster C sub n sup +, the dominant fragment observed is C sub n-3 sup +. Fluence dependence measurements of photofragmentation yield bracketed dissociation thresholds, photofragmentation cross sections and product branching ratios. Photodissociation with 248 nm light is found to be primarily linear with laser fluence for n>5, but there are indications that C sub 3 sup + and C sub 5 sup + fragment only with the absorption of two or more photons. For 351 nm light, clusters with six or more atoms all show a linear dependence. The photofragmentation cross sections for both 351 nm and 248 nm light show a significant change as a function of cluster size.