Low Ion Velocity Slowing Down in a Demixing Binary Ionic Mixture

We consider ion projectile slowing down at low velocity Vp $<$ Vthe, target electron velocity, in a strongly coupled and demixing hydrogen-helium ionic mixture of mostly astrophysical concern. It is investigated in terms of quasi-static and critical charge-charge structure factor [1]. Non-polarizable as well as polarizable and partially degenerate electron backgrounds are successively given attention. The focussed low ion velocity slowing down [2] turns negative in the presence of long wavelength and low frequency hydrodynamic modes,thus signaling a first order critical demixtion. Such a process actually documents an energy transfer from target ion plasma to the incoming ion projectile, i.e a superelastic process. \\[4pt] [1] D.Leger and C.Deutsch, PRA 37, 4916, 4930 (1988)\\[0pt] [2] B.Tashev et al, PoP 15, 102701(2008)