Relative yield ofC60−in hyperthermal surface scattering of neutralC

Abstract

The yield of C 60Ϫ negative ions following scattering of neutral C 60 molecules from a graphitized ͑monolayer-covered͒ nickel surface was measured under near-normal-incidence conditions as a function of the hyperthermal impact energy. An increase of two orders of magnitude was observed for the impact energy range of 4-42 eV. Energy and angle distributions of both scattered ions C 60 Ϫ and neutrals C 60 0 were also measured and compared for this impact energy range. We show that the C 60 Ϫ yield obeys an exponential dependence on the inverse of the outgoing normal velocity component similar to that observed before for charge exchange in atom-surface collisions. This dependence is demonstrated here for the very low normal velocity range of (0.33-1.25)ϫ10 5 cm sec Ϫ1 . We have analyzed the experimental results using simple models for the negative ion formation probability and the resonance tunneling rate of the active electron between C 60 and the surface, and obtained a critical ''ion formation'' distance Z C ϭ11-12 Å. This value is in reasonable agreement with the value Z C ϭ13Ϯ1 Å extracted before from independent measurements of image charge effects on energy and angular distributions of the negative ion C 60 Ϫ as compared with the neutral C 60 0 under near-grazing-incidence conditions. The picture emerging from the experimental observations is consistent with a complete memory loss of the initial charge state along the incoming trajectory of the hyperthermal particle. The C 60 -surface system is shown to behave adiabatically up to a remarkably large distance from the surface.

Velocity correlated emission of secondary clusters by a single surface impact of a polyatomic ion: a new mechanism of cluster emission and subpicosecond probing of extreme spike conditions

“…44 Most measurements were done over a broad impact energy range from 10 eV to 20 keV. These included for example hyperthermal scattering of the neutral C 60 , 45,46 ion-surface collisions at sub keV impact 47,48 leading to complete shattering at near-normal collisions, charge exchange 49,50 and grazing incidence measurements. 51,52 The C 60 + ion also played a role as a leading projectile in organic SIMS and molecular depth profiling at 10–20 keV collisions.…”

Effect of target surface on the elastic properties of fast fullerenes

“…In the case of a stiff/soft molecule, a small/large amount of the energy is transferred to internal degrees of freedom and the outgoing kinetic energy is large/small. During the last two decades, a fair number of studies have been devoted to elastic properties, stability, fragmentation, and charge transfer during scattering of hyperthermal fullerenes from surfaces [15][16][17][18][19][20][21][22]. However, for angles of incidence Φ in ≥ 10…”