P. Barone

The excitation of collective electronic modes in Al by slow single charged Ne ions

Abstract We have studied electron emission from decay of plasmons excited in the interactions of slow single charged Ne ions with Al surfaces as a function of incident energy ranging from 0.7 to 8 keV. Bulk plasmon excitation occurs above a threshold incident energy of ∼1 keV and initially coexists with potential excitation of surface modes. The excitation of bulk plasmons in Al is determined by fast electrons traveling inside the solid.

Plasmon excitation in Al by keV Ne and Ar ions

Abstract We present experimental studies of plasmon excitation by keV Ne and Ar single charged ions on Al surfaces. Plasmons are identified through the characteristic energy spectrum of electrons from plasmon decay. At 1 keV incident energy, surface plasmons are excited by Ne+ but not by Ar+. For higher energies we observe bulk plasmon excitation resulting, most likely, from excitation by fast electrons, such as Al-2p Auger electrons, traveling inside the solid.

Bulk and surface plasmon excitation in the interaction of He+ with Mg surfaces

Abstract We report on studies of plasmon excitation in Mg under the impact of slow He + ions in the incident energy range 0.1–0.5 keV. Consistent with studies on Al surfaces, a transition from surface to bulk plasmon excitation occurs as the energy of the ion is increased. Previous methods in the literature to obtain information about yields of electron emission from plasmon decay are discussed. A new data analysis procedure is presented, which allows disentangling the contributions to the experimental spectra arising from different emission mechanisms, showing that potential excitation of multipole surface plasmons gives an important contribution to electron emission.

Bulk plasmon excitation in the interaction of Ne+ and Ar+ ions with polycrystalline Al surfaces

Abstract We report experimental studies of electron emission from decay of bulk plasmons excited in the interaction of slow single charged Ne and Ar ion with polycrystalline Al surfaces. To answer the question of whether bulk plasmons can be excited by charged particles moving outside the surface, we performed measurements as a function of emission angle. Our experiments show that bulk plasmon excitation occurs inside the solid for incident ion energies above a threshold of ∼1 keV. Bulk plasmon excitation in Al by keV single charged Ne and Ar ions is caused by fast electrons traveling inside the solid, which are energized in collisions initiated by the projectile.

Sub-threshold plasmon excitation in free-electron metals by helium ions

Abstract In this work, we re-examine sub-threshold plasmon excitation by ions measuring the energy distributions of electrons emitted from Al and Mg under the impact of 0.16–4 keV single charged Helium ions. Electron energy distributions for the case of He+ projectiles contain well distinguished structures that confirm the excitation of multipole surface plasmons, due to the potential energy released by the neutralization of incoming ions. It is shown that electron emission from multipole plasmon decay is more intense than from Auger neutralization (AN). Our experiments indicate that scattering and cascade in the solid of electrons excited by plasmon decay and by AN may give an important contribution to electron emission.