Classical trajectory calculations for collision energy dependence of partial Penning ionization cross-sections (CEDPICS) of He*(2(3)S) + (N-2,CO) were performed to obtain molecular orbital (MO) functions based on the observed data; coefficients in linear combination of atomic orbitals and orbital exponents for a minimal atomic basis set (STO-6G) were optimized in order to give good agreement between observed and calculated CEDPICS. Although a crude basis set was assumed, obtained MOs derived by experimental CEDPICS were found to be very similar in the outer characteristics to theoretically obtained SCF-MOs in terms of much larger basis sets (6-311 + G*). (C) 2004 Elsevier B.V. All rights reserved.