A first principles description of electronic excitation in Li-He colliding pairs is developed introducing l-dependent pseudopotentials and including two- and three-body polarization terms. The treatment combines an eikonal approximation and time-dependent molecular orbitals to provide interatomic potentials, their non-adiabatic couplings, and state populations during interactions. We discuss the effects of the basis set size on the calculations, and compare our results with experiment and other calculations. Our integral cross-sections obtained with a large basis set are in excellent agreement with experiment. (C) 2002 Elsevier Science B.V. All rights reserved.