Slow Li + He Collisions: A Molecular State Treatment

Low-energy state-changing cross sections involving the ground state of He atoms and ground states of Li atoms are calculated using the semiclassical impact parameter close-coupling method based on a molecular states expansion to represent the electronic wave function. The plane wave translation factor is used considering a classical trajectory for the motion of the heavy particles. We approximate this many electrons system to a one-electron problem by using the l-dependent pseudopotential technique. In order to obtain cross sections, we retain nine molecular states including six and three states in our close coupling calculations, but, in the structure calculations, we have included 16 states (ten and six states) so the excitation of 5s levels of the target Li atoms is possible. Our cross sections for Li (2p) excitation agree well with previous theoretical and available experimental results.