Multireference CI calculations of radiative transition probabilities between low lying quartet states of the C2+ ion

Potential energy functions for the ten lowest electronic states of the C₂⁺ ion have been calculated from correlated CASSCF and MC-CI electronic wavefunctions and used for derivation of the spectroscopic constants. The predicted values are expected to be accurate within 0.01 Å for R_e, 20–30 cm⁻¹ for ω_e and 0.05–0.1 eV for T_e. For the three lowest quartet states the electronic transition moment functions have also been calculated. For the transitions among these states, radiative lifetimes and absorption oscillator strengths are given which should be accurate within about 15%.