<正>Plenty of dynamical information was carried by recoil ion in the ion-atom collision.Employing recoil-ion momentum spectroscopy (RIMS), we have performed the experiment of He2+ on argon collision at 7. 5 keV/u, which can give both the various reaction channels and the final recoil momentum vector, and from which detailed information of the dynamics can be deduced. The experimental set-up has been described elsewhere.