Analytical representations of high level ab initio potential energy curvesof the C-2 molecule

Realistic analytical representations of the twelve lowest singlet and tripl et electronic adiabatic potential energy curves of C-2 molecule are given i n this article. The corresponding electronic states are correlated with C a toms both in their P-3 state, A ew set of high level MRCI calculations coup led with a double many-body expansion analytical fitting based on the exten ded Hartree-Fock approximate correlation energy model have been used in thi s work. Using RKR data available in the literature, comparison is made betw een our results and RKR turning pints concerning the four lowest singlet st ates X(1)Sigma (+)(g), A(1)Pi (u), B(1)Delta (g), and B(11)Sigma (+)(g) of C-2. The agreement is very satisfying. (C) 2000 Elsevier Science B.V. All r ights reserved.