Generation of Surface Plasmons under Slow Ion Impact

Slow multicharged ions recombining at a solid surface set free potential energy which can cause the ejection of electrons (potential emission/PE) and heavy particles (potential sputtering/PSI, for non-metals only). Whereas especially for metallic targets the PE process is now reasonably well understood, for the PSI process at particular insulator surfaces first qualitative explanations have just been put forward. There are some hints that part of the available potential energy is also spent for excitation of collective oscillations of the target electron gas (plasmons). By measuring the energy distribution of slow electrons ejected from atomically clean single-crystalline metal surfaces under impact of slow singly and multiply charged ions (MCI), we seek to explore the role of surface- and bulk plasmon excitation in competition with MCI induced PE and lateron also MCI induced PSI. Such studies should also clarify the contribution from fast Auger electron-induced secondary electron emission to MCI induced PE, if projectile inner shell vacancies develop during the hollow atom phase near and at the surface, giving rise to fast projectile Auger electrons. Special emphasis will be devoted to comparative studies for different target surfaces.