Sum rules and the photoabsorption cross sections of C60

The absolute photoabsorption spectrum of C-60 is constructed from experimental data, by linking relative measurements to some recent absolute determinations. Sum rule analysis supports these recent determinations over earlier ones, but substantially better agreement is achieved with similar to 20% reduction in the cross-sections. Attention is focused on the 11-40 eV region, where discrepancies exist in both pseudophotoabsorption and photoionization data. Some inferences are drawn regarding the propensity of large molecules such as C-60 toward multiple ionization, rather than photodissociative ionization. Problems encountered with prior application of quasi-equilibrium theory to the dissociative ionization of C-60 are discussed. (C) 1999 American Institute of Physics. [S0021-9606(99)01728-6].