ELECTRON-EMISSION YIELD OF AL, CU, AND AU FOR THE IMPACT OF SWIFT BARE LIGHT-IONS

The electron emission yield induced by mega-electron-volt H+, He2+, Li 3+, B5+,, and C6+ impact on aluminum, copper, and gold targets was mea sured. We found a significant deviation of the results from a simple p roportionality to the stopping power, especially for heavier ions and low projectile velocities. Using a slightly modified model by J. E. Bo rovsky and D. M. Suszcynsky [Phys. Rev. A 43, 1433 (1991)] our experim ents could be well represented. In this model the collective electric held generated along the projectile's path was taken into account. Con sequently, the positive ion channel appears to be the dominant mechani sm that leads beyond a projectile-independent yield-to-stopping power ratio.