PHASE EFFECT IN THE ENERGY-LOSS OF HYDROGEN PROJECTILES IN ZINC TARGETS

We present an experimental and theoretical study of the phase effect i n the energy loss of fast hydrogen beams colliding with gas and solid zinc targets. The experiments show a maximum phase effect of 50% aroun d 50 keV/u, the energy loss per atom in the solid target being smaller than in the gas target. An extensive theoretical study of all the pro cesses contributing to the energy loss in the two phases shows that th e experimental findings can be explained primarily by the screening of the projectile field by the valence electrons in the solid.