Angular dependence of vibrational excitation in Li+^{+} + N2_{2}, CO collisions at medium energies

We have measured the vibrational populations of N$_{2}$(X) and CO(X), produced by Li$^{+}$ projectiles, at collision energies $100\leq E\leq 500$ eV as a function of the scattering angle. Though vibrational excitation is a weak process in the angular range studied, it is found to strongly vary with the angle. Other inelastic processes such as charge exchange or electronic excitation are negligible. A theoretical model developed previously to describe vibrational excitation in this energy range is applied to the considered collisional systems. The reasonable agreement with experiment thus obtained shows that the observed vibrational excitation results only from ground state interactions