PHOTOELECTRON-SPECTROSCOPY OF C-4(-), C-6(-), AND C-8(-)

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