15min:

DAMIAN L. KOKKIN, GEORGE B. BACSKAY AND TIMOTHY W. SCHMIDT, School of Chemistry, University of Sydney, NSW 2006, Australia.

High level ab initio calculations were carried out on the X^{1 +}_g, A¹ _u, a³ _u, b^{3 -}_g, c^{3 +}_u and d³ _g levels of the C₂ radical. Calculations were carried out at the MRCI level with full-valence CASSCF reference wavefunctions and basis sets up to aug-cc-pv6z. The resulting wavefunctions and potential energy surfaces were employed to calculate Einstein coefficients for allowed transitions and intercombination bands. These values were used to model the behaviour of the C₂ system in interstellar and circumstellar environments, paying particular attention to the Red Rectangle (HD 44179).