A THEORETICAL INVESTIGATION OF 4 ELECTRONIC STATES OF C-6(-) AND THE GROUND-STATE OF LINEAR C-6

Large-scale open-shell coupled cluster calculations have been carried out for the four lowest doublet states of C-6(-) and the ground state of linear C-6. They strongly support the assignment of the peaks at 607.7 and 586.5 nm observed in neon matrix isolation experiments to the 0(0)(0) and 3(0)(1) transitions within the electronic band (C) over tilde (2) Pi(g) <-- (X) over tilde (2) Pi(g) of C-6(-). The vibrational structure of the photoelectron spectrum of C-6(-) has been calculated; the 1(0)(1) transition is calculated to have 42% intensity with respect to the adiabatic peak. Some misassignments of the experimental threshold photodetachment and autodetachment spectra are corrected. Excellent agreement with experiment is obtained for the electron affinity of linear C-6.