PROJECTILE DEPENDENCE OF ION-INDUCED ELECTRON-EMISSION FROM THIN CARBON FOILS

The total secondary-electron yield from thin carbon foils traversed by heavy ions has been measured as a function of the projectile atomic number Z(p), the initial charge state, and the incident velocity. For nearly all projectiles in the velocity region studied the number of emitted electrons per incoming projectile gamma and the stopping power S have, as expected, the same velocity dependence. However, for ions with Z(p) > 29 a slight increase of the ratio LAMBDA = gamma/S with the projectile energy is observed. A systematic study of the ratio LAMBDA as a function of the projectile atomic number Z(p) indicates a Z(p)-0.2 dependence of the parameter LAMBDA. Possible explanations for this Z(p)-0.2 dependence of the LAMBDA parameter are given.