Analytical representations of high level ab initio potential energy curves of the C2 molecule

Realistic analytical representations of the twelve lowest singlet and triplet electronic adiabatic potential energy curves of C-2 molecule are given in this article. The corresponding electronic states are correlated with C atoms both in their P-3 state, A ew set of high level MRCI calculations coupled with a double many-body expansion analytical fitting based on the extended Hartree-Fock approximate correlation energy model have been used in this work. Using RKR data available in the literature, comparison is made between our results and RKR turning pints concerning the four lowest singlet states 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 rights reserved.