Electron Emission Induced by Atomic Collisions
División Colisiones Atómicas - Centro Atómico Bariloche
8400 San Carlos de Bariloche, Río Negro, Argentina
Tel: +54 2944 445220 Fax: +54 2944 445299
Permanent staff
Guillermo BERNARDI,
e-mail
Pedro FOCKE ,
e-mail
Alejandro GONZALEZ,
e-mail
Sergio SUAREZ,
e-mail
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Research fellows
Sergio MARTINEZ,
e-mail
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Topics of research
This research group is involved in the experimental study of electron emission
produced during collision of atomic and ionic projectiles on gaseous or solid-foil
targets. The activity is mainly oriented to the measurements of spectra of
electron energy and angle of emission. The information obtained, expressed in the
form of double differential cross sections, is a valuable tool for the description
of interactions that take place in atomic systems. This research field
started in our group in the early 70's and is still under full activity
and continuous development. The main topics investigated in recent years are:
- The detailed study of "cusp electrons", also known as "convoy electron mechanism".
- Complete measurements of double differential cross sections at intermediate collision energies for light projectiles.
- Correlated projectile and target emission processes known in the literature as "two-center effects".
- Detailed study of spectra at very low electron energies or "soft-collision mechanism".
- The "neutral-projectile cusp electrons" and "diffraction effects" in electron loss collisions.
- Full spectra measurements for the "transfer ionization" mechanism in simple collision systems.
- At present time we started the study of molecular-fragmentation mechanisms at intermediate collision energies.
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Collaboration with other laboratories
Horst Schmidt-Bocking and Karl Ontjes Groeneveld
Instituto de Fisica Nuclear de Frankfurt (IKF) de la Univerdidad
J. W. Goethe, Germany.
Lazlo Sarkadi
Instituto de Fisica Nuclear de Debrecen, Hungria (ATOMKI).
Eduardo Montenegro and Geraldo Sigaud
Universidad Catolica de Rio de Janeiro, Brazil
Nelson de Castro Faria
Universidad Federal de Rio de Janeiro, Brazil
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Experimental facilities
The experimental facility available to our group to perform the mentioned
research is an experimental line for electron spectroscopy installed in the
"Kevatron" accelerator laboratory. In this line there is mounted an electrostatic
electron analyzer that allows the measurement of electron energies for all
emission angles of interest for a collisional experiment with axial symmetry.
The salient feature of this instrument is the capability to perform measurements
at emission angles close and at the projectile beam direction. The energy
resolution of the instrument ranges from 1 to 6%. It can be used to analyze
electrons and ion fragments as well. As detector we use a channeltron. This
instrument was designed and fully built in our machine shops. The analyzer
is mounted in a chamber with a target produced by a crossing gas beam effusing
from an hypodermic needle (optionally one can mount a thin foil instead when
performing ion-foil measurements). Before entering the collision chamber, the
ionic beam is collimated by a set of adjustable slits. The addition of a gas
chamber for charge-interchange collisions can be used to produce a neutral
projectile beam. The beam emerging from the collision region can be monitored
and/or measured with a Faraday cup. Instead of the beam monitor a charge- state
electrostatic deflector system together with two projectile detectors is used to
measure electron spectra for different final charge-states. The scanning of
electron energies or emission angles during spectra measurements is completely
automatized with computer controlled equipment. Coincident as non coincident
measurement techniques are usual in the operation of this facility.
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This page is maintained by: E.A. Sánchez
Last update: April, 2001