Photoelectron spectroscopy of C-4(-), C-6(-), and C-8(-)

Photoelectron spectra of C-4(-), C-6(-), and C-8(-) were obtained at two photodetachment wavelengths, 266 nm (4.657 eV) and 213 nm (5.822 eV). The spectra reveal considerably more electronic and vibrational structure than was seen in previous studies of these species [D. W. Arnold et al., J. Chem. Phys. 95, 8753 (1991)]. Term values for several low-lying excited electronic states of the neutral carbon clusters have been obtained, as well as new vibrational frequencies for the ground and some of the excited electronic states of the neutral clusters. The assignments of excited electronic states were aided by measurements of the photoelectron angular distributions. A new assignment of the vibrational frequencies for C-6 is in considerably better agreement with ab initio results than our original assignment. (C) 1997 American Institute of Physics.