The radiative lifetime of A 1Πu C2

This note reports ab initio potential curves of A 1Πu and X 1Σ+g states of C2, and the A–X radiative lifetimes. The calculations are based upon configuration interaction wave functions formed from single and double electron excitations from state-averaged MC-SCF reference functions expanded in a Gaussian basis. The lifetimes for (J′=1,v′) A 1Πu are calculated to be about 25% longer than those found in previous ab initio works, but about 25% shorter than the most recent LIF measurements of Bauer, Becker, Bielefeld, and Meuser. Also reported are the quadrupole moments of the A 1Πu and X 1Σ+g states as a function of internuclear distance and the quadrupole lifetimes of several (v′=0,J′) levels in the X state.