A theoretical description of multi-channel fragmentation of the Naq cluster-ion in collision with a He target

q Ž . Fragmentation of the Na cluster-ion in collision with He in the 100 eV centre of mass energy range is investigated 3 theoretically. The dynamics study is split into two stages: the He–Naq encounter itself and the post-collisional motion of the 3 Naq cluster-ion. The first stage is treated semiclassically and involves a ‘frozen cluster approximation’. The second stage is 3 treated by a trajectory surface hopping procedure. The two stages make use of diabatic and adiabatic representations, respectively and involve diatomics-in-molecules calculations. For the He–Naq system, an adaptation of the DIM approach 3 incorporating three-centre integrals is employed. Different fragmentation mechanisms are discussed and comparison with experiment is made. q 1999 Elsevier Science B.V. All rights reserved.