Potential energy and transition dipole moment functions of C-2(-)

The potential energy curves of C2- in its 2 Sigma g+, 2 Pi and 2 Sigma u+ states are constructed by morphing the appropriate icMRCI ab initio curves within the framework of the reduced potential curve (RPC) approach of Jenc and Pliva. The actual morphing is performed by fitting the RPC parameters to available experimental data. The resulting potential energy curves are in close harmony with these data thus allowing for evaluation of highly accurate wavefunctions of the observed rovibronic molecular states and for reliable interpolation of the so-far unobserved states. Using these wavefunctions and theoretically evaluated electronic transition moment functions, the dipole moment matrix elements are calculated for the allowed transitions among the studied vibronic states. The 2 Sigma g+ potential energy curve is also used for predicting rotational energies of 13C12C-. The calculated data are believed to be useful in searching for spectral evidence of C2- both in the laboratory and interstellar medium. Several rotational lines of the nu = 0-1 vibronic band of the B22 Sigma u+ rarr X22 Sigma g+ transition are shown to be coincident with absorption features in the spectrum of the carbon star HD 56126.