Excitation of electrons from an Al surface by grazing-angle-incident fast heavy ions

Abstract

Measurements were made, at various emission angles, of energy spectra of electrons from Al induced by grazing-angle-incident ions of N 6+ , Ar l2+ , and Xe 27+ with equal velocities corresponding to 0.98 MeV/amu. A new line which could not be explained by any of the hitherto identified mechanisms was observed at an energy obviously larger than that of an electron with a velocity equal to the projectile. The projectile and emission-angle dependences of the line are consistent with the dynamic-imagepotential acceleration mechanism.

Dynamical image potential and induced forces for charged particles moving parallel to a solid surface

“…Then, one could expect that in this type of experiment the (repulsive) perpendicular force on the electrons, due to the dominant field induced by the ion, will produce a deviation of the angular distributions of the emitted electrons away from the surface; this effect should be more important at lower velocities. This also seems to be at least in qualitative agreement with observations of the angular dependence at high and low velocities in different experiments [27,30,31]. In addition, in Ref.…”

Indications of Nuclear-Track-Guided Electrons Induced by Fast Heavy Ions in Insulators

“…For high Z p it is possible that solid-state potentials saturate and/or that the convoy electron cloud is compressed near the nucleus leading to an over-proportional projectile attraction. Previous investigations indicate that the acceleration observed for the conducting target is due to the influence of the image potential of the projectile/convoy-electron system [7,8]. In fact, for low projectile charges the calculated image potential (solid line [14,15]) is consistent with the shifts measured for C foils.…”

“…In both cases convoy electrons are produced by electron capture (ECC) [3] and by electron loss to continuum states of the projectile (ELC) [4,5]. In dense matter, these electrons are subject to a random walk under the influence of the target constituents and the projectile potential [6].Convoy electrons can be accelerated by the imagepotential of the projectile charge, as has been found for ions under glancing-angle scattering conditions at semiconductor and metal targets [7][8][9] and at normal-incidence conditions for highly charged ions at a proton-equivalent energy of 5 MeV͞u [10]. In ion-insulator interactions ionizing collisions result in a positive nuclear-track potential, which can decelerate target Auger-electrons emitted from the insulator surface [11] and accelerate desorbed positive hydrogen ions [12].…”

Solid-state effects in electron emission from atomic collisions near surfaces

“…Concurrently, a shift of the CEP to electron velocities larger than vP was proposed [6] and independently measured [4] for projectile charges greater than one. Subsequently, large shifts of up to lOOeV have been observed in several laboratories [7,8,9,10,11,121.…”