Momentum spectroscopy in ion-atom collision

In this article, we review the recent progress in the field of momuntum spe ctroscopy in fast-ion atom ionization based on the measurements of electron double differential cross section (DDCS). It is shown that the energy and angular distributions of the low energy electron emission not only provide informations on two center effects but also can be used to study the final- state longitudinal momentum distributions of the electrons, recoil-ions and projectiles. To demonstrate this we have used the recently measured data o f low energy electron DDCS for three collision systems: C6++He/H-2 (upsilon = 10) and p+H (upsilon = 2.14). The complementary nature of the electron s pectroscopy and the recoil-ion momentum spectroscopy (RIMS) have been inves tigated using a new formulation based on three-body kinematics to explore t he ionization dynamics in detail. The separation of the soft and hard colli sion branches of recoil-ion distributions is a novel feature of the present technique. Atomic units are used unless specified.