INVESTIGADORES
GARCIA evelina Andrea
congresos y reuniones científicas
Título:
Experimental and theoretical study of Hydrogen scattering from a Graphite surface
Autor/es:
F. BONETTO; EVELINA A. GARCÍA; R. VIDAL; J. FERRÓN; E. C. GOLDBERG
Lugar:
San Carlos de Bariloche, Río Negro, Argentina, November 6-10
Reunión:
Conferencia; 13th International Conference on Solid Films and Surfaces (ICSFS-13); 2006
Resumen:
The efforts made in
trying to understand how Hydrogen interacts with solids are based, besides its
intrinsic basic interest, on its importance as a clean and renewable source of
energy. The energy range of interest is, on the other hand, extremely wide
going from the static one in the H storage devices, up to thousands of keV in
the fusion reactors. Within this last
case, the interaction of energetic H with C seems to be the most interesting
combination since graphite is considered the first choice as wall material in
magnetically confined fusion devices.
In the present work, we
perform both theoretical and experimental studies of the ion formation during
positive H ion scattering on Highly Oriented Pyrolitc Graphite (HOPG), for a
wide range of incoming energies and incident and outgoing angles.
Ion scattering
spectrometry with time of flight analysis is employed to measure the ion
fraction in H+ projectiles scattered from a well characterized HOPG
surface at two fixed scattering angles: 45o and 135o. For
both scattering angles and after analyzing the time of flight spectra, the ion
fraction is determined for several incident energies (in the low keV range) and
outgoing angles.
In
the theoretical approach, the adsorbate-substrate interacting system is
adequately described by means of an Anderson like Hamiltonian where the valence
and core surface states are included. Under the previous assumption of a rapid
neutralization of H+ projectiles (mainly related with a resonant
electron capture), the positive and negative ionization probabilities can be
calculated by employing a Green's function formalism to solve the dynamic
collisional process.
Both
theoretical and experimental results are analyzed and contrasted for a fixed
set of parameters: incident energy, scattering and outgoing angles. The
dependence of the scattered ion fractions with these parameters, and the effect
of the semi-metal character of Graphite (HOPG) in the negative ion formation,
are specially analyzed.