Slow photoelectron imaging spectroscopy of CCO- and CCS-.

High-resolution photodetachment spectra of CCO(-) and CCS(-) using slow photoelectron velocity-map imaging spectroscopy are reported. Well-resolved transitions to the neutral X (3)Sigma(-), a (1)Delta, b (1)Sigma(+), and A (3)Pi states are seen for both species. The electron affinities of CCO and CCS are determined to be 2.3107+/-0.0006 and 2.7475+/-0.0006 eV, respectively, and precise term energies for the a (1)Delta, b (1)Sigma(+), and A (3)Pi excited states are also determined. The two low-lying singlet states of CCS are observed for the first time, as are several vibronic transitions within the four bands. Analysis of hot bands finds the spin-orbit orbit splitting in the X (2)Pi ground state of CCO(-) and CCS(-) to be 61 and 195 cm(-1), respectively.