PHASE EFFECT IN THE ENERGY-LOSS OF H PROJECTILES IN ZN TARGETS - EXPERIMENTAL-EVIDENCE AND THEORETICAL EXPLANATION

The energy loss of H projectiles in solid and gaseous Zn has been measured for the first time down to 20 keV/u, showing large differences in the stopping cross section depending on the state of aggregation of the target. For 25-keV protons, the stopping cross section of Zn in the gas phase is found to be 60% higher than that in the solid phase. A charge-state approach to the stopping power of ions in the solid and in the gas is successful in explaining this effect.