Bound electronic states X-1 Sigma(+), a(3)Pi and A(1)Pi of C2B-

Large-scale electronic structure calculations were performed to generate a three-dimensional potential energy function for the X(1)Sigma(+) state of C 2B-. Spectroscopic constants and anharmonic re-vibrational levels were calc ulated variationally and by perturbation theory using this function. The gr ound state possesses an equilibrium geometry with R-e(CC) = 1.270 Angstrom and R-e(CB) = 1.461 Angstrom, the fundamental vibrational transitions are p redicted at v(1)(CB)(J = 0) = 1014.7 cm(-1), v(2)(J = 1) = 125.4 cm(-1) and v(3)(CC)(J = 0) = 1935.4 cm(-1) (exp. 1936.3 cm(-1)). The difference elect ron density plot showed that the negative charge is almost entirely localiz ed in the boron lone pair and the BC bond region. The A(1)Pi-X Sigma(+) T-e excitation energy was calculated to be 23 722 cm(-1) confirming the assign ment made for the transition detected at T-o = 23 131 cm(-1) in a neon matr ix. For the A (1)Pi state an equilibrium geometry with R-e(CC) = 1.324 Angs trom and R-e(CB) = 1.396 Angstrom was obtained. The vertical excitation ene rgy of the a (3)Pi-X (1)Sigma(+) transition is predicted at 15 306 cm(-1). Both excited states lie below the vertical detachment energy calculated at 25 845 cm(-1).