Anisotropic potential energy surfaces were optimized for classical trajectory calculations in order to reproduce collision energy dependence of partial Penning ionization cross-sections for N-2 and CO molecules with a He*(2(3)S) atom. Ab initio model potentials using a Li(2(2)S) atom in place of a He*(2(3)S) atom based on the similarity of valence electronic configurations were found to be successfully corrected by addition of negative terms including an exponential function combined with Legendre expansions. Optimized sets of parameters demonstrate that the most important correction terms are related to attractive interactions due to electron transfer from He*(Li) to unoccupied molecular orbitals. (C) 2002 Elsevier Science B.V. All rights reserved.