Colloids and Surfaces
A: Physicochemical and Engineering Aspects 208 (2002) 103 – 114
Collisions of fullerenes with surfaces at the 5–100 eV
impact energy range
E. Kolodney *, B. Tsipinyuk, A. Bekkerman
Department of Chemistry, Technion – Israel Institute of Technology, Haifa 32000, Israel
Received 11 June 2001; accepted 5 November 2001
Abstract
In this paper, we will present recent studies on the scattering dynamics of neutral and charged fullerenes from
surfaces at the hyperthermal impact energy range. The energy range for the neutral colliders is 5 – 50 eV (aerodynamic
acceleration in seeded beams) while with negatively charged ions we extend it up to 100 eV. The smooth overlap of
the two energy regions using neutral and charged C
60
is demonstrated. The translational energy of the scattered
particles (both C
60
0
and C
60
-
) was found to scale linearly with impact energy for both near normal and near grazing
scattering angles. Kinetic energy losses varied with scattering angle from 15% (near normal incidence) to 40%
(near grazing incidence). Analysis of the results in terms of simple kinematical models demonstrates nearly complete
decoupling between normal and tangential energy losses. Furthermore, the accuracy of our energy measurements
( 0.1 eV) enables us to extract, for the first time, molecule – surface binding energies from kinetic energy losses
measured in molecular beam – surface scattering experiments. We compare this dynamically determined value with the
equilibrium one as measured by temperature-programmed desorption experiments. The yield of C
60
-
negative ions
following scattering of hyperthermal neutral C
60
molecules from a graphite monolayer on nickel surface (Ni/C) was
measured as a function of impact energy. An increase of two orders of magnitude was observed going from 4 to 42
eV. Energy and angle distributions of both scattered ions (C
60
-
) and neutrals (C
60
0
) were measured and compared for
this impact energy range. The C
60
-
ion yield was found to obey an exponential dependence on the inverse of the
outgoing normal velocity component similar to that observed before for atom – surface collisions at much higher
energies. The shifts observed between the angular and energy distributions maxima of the neutral and negative ion
could be analysed and explained in terms of image charge effects on the outgoing trajectory (deflection) and exit
energy (retardation) of the C
60
-
. A large critical distance for ion formation was extracted from the results. The charge
transfer dynamics is consistent with final charge state exclusively determined along the exit trajectory. © 2002 Elsevier
Science B.V. All rights reserved.
Keywords: Fullerenes; Electron transfer; Surface scattering
www.elsevier.com/locate/colsurfa
Submitted to the special issue of ‘Colloids and Surfaces’ devoted to the Polish – Israeli Symposium on ‘Current Trends in
Interface Chemistry’, Poland 2000.
* Corresponding author. Fax: +972-4-8233735
E-mail address: eliko@techunix.technion.ac.il (E. Kolodney).
0927-7757/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII:S0927-7757(02)00106-1