Vector correlations in dissociative charge transfer induced in He+-O-2, N-2 collisions at medium energies

The dissociative ionization of O-2 and N-2 molecules following electron cap ture in He+-O-2, N-2 collisions has been investigated in the keV energy ran ge with a new device which combines imaging and time-of-flight resolved coi ncidence techniques, The (VHe+. V-He. VO+(N)+) velocity vector correlation consists of measuring the V-He and VO+(N)+ velocities of the He scattered n eutral and O+ (N+) fragment ion produced by the same collision event, for a well defined VHe+ incoming projectile velocity. It leads to a kinematicall y complete analysis of the collision. The subsequent kinetic energy correla tion provides direct identification of all the quasi-resonant, exoergic and endoergic processes in terms of their reaction pathway, namely the interme diate molecular ion excited state in the Franck-Condon region and the corre sponding dissociation limit. The spatial analysis of the velocity vector co rrelation for the dissociative ionization events enables us to investigate for each process the dependence of the electron capture probabilities upon the alignment of the molecular axis with respect to the VHe+ collision velo city and to the collision plane. Significant spatial anisotropies are obser ved for the endoergic process involving the excitation of the N-2(+) (F (2) Sigma (+)(g)) State in He+-N-2 collisions at 1.5 and 3 keV, and visualized in the (chi (c), phi (c)) angular correlation diagram, where chi (c) and p hi (c) are the polar and azimuthal angles which characterize the molecular axis orientation in the collision frame.