Photodissociation and radiative processes in interstellar C2

Ab initio methods are used to compute photodissociation and radiative processes occurring in interstellar C 2 from the X 1 Sigma g + ground state. To this end, self-consistent-field+configuration interaction wavefunctions and potential energy curves of the X 1 Sigma g + and the first four 1 Pi u states and transition moments between the ground and excited electronic states are computed. Photodissociation cross sections for absorption into the second and third 1 Pi u states are calculated and the corresponding interstellar photodissociation probability is found to be 0.73*10 -10 s -1 . Ground-state transition probabilities and absorption oscillator strengths f 00 of the Phillips (A 1 Pi u -X 1 Sigma g + ) and 2 1 Pi u -X 1 Sigma g + systems are determined.