Ab initio study of the 1 2Delta-X 2Pi electronic transition of C2As.

We report the results of ab initio calculations on the 1 (2)Delta-X (2)Pi spectral system of C(2)As. The present study is closely related to the recent comprehensive experimental and theoretical work by Wei et al. [J. Chem. Phys. 129, 134307 (2008)]. By means of the state-average complete active space self-consistent field and multireference configuration interaction approach, we computed the vertical excitation energies to the low-lying doublet electronic species, potential surfaces and spin-orbit constants for the X (2)Pi and 1 (2)Delta states, as well as the components of the electric dipole moment for the transition between these two species. Using these data, we calculated the vibronic energy levels, the spin-orbit structure of the spectrum, and the vibronic transition moments of the X (2)Pi-1 (2)Delta system. The results of the present study for the X (2)Pi state agree with those derived from experimental findings by Wei et al., they elucidate the vibronic and spin-orbit structure in the 1 (2)Delta species, and offer predictions for experimental searches of heretofore unobserved electronic states.