A (2)SIGMA(-X-2-PI ELECTRONIC ABSORPTION-SPECTRUM OF CCO- IN A NEON MATRIX()[)

An electronic absorption spectrum of CCO- isolated in a neon matrix ha s been observed. The matrix was prepared by co-deposition of the mass- selected anions with excess neon at 6 K. The observed absorption spect rum is assigned to the A (2) Sigma(+) <--X (2) Pi electronic transitio n of linear CCO-on the basis of mass-selection, photobleaching behavio r, comparison with ab initio calculations, and the discernible vibrati onal structure. The origin band is located at 817.4(2) nm and the fund amental frequencies in the A (2) Sigma(+) state are nu(1)(sigma(+)) = 2082(3), nu(2)(pi) 656(3), and nu(3)(sigma(+))=1185(3) cm(-1). The nu( 1) fundamental in the electronic ground state has been observed at 187 6.7(1.0) in the infrared spectrum.