3.1
Ionization of neon by intermediate energy carbon ions
S.L. McLawhorn a) , L.H. Toburen a) , J.L. Shinpaugh a) , E.L.B. Justiniano a) , M. Dingfelder a) , K.
Tőkési, B. Sulik, P. Sigmund b) , A. Schinner c) , C. Reinhold d) , D. Schultz d)
During the past few years there has been
increasing interest in ionization of atomic
and molecular targets by intermediate-energy
dressed and partially dressed ions. These systems are particularly challenging to describe
theoretically owing to screening of the projectile nuclear charge by bound electrons, interactions of projectile electrons with target electrons, and the large number of possible exit
channels. At ECU we have initiated measurements of the doubly-differential ionization
cross sections, differential in ejected electron
energy and emission energy, for carbon ions of
different initial charge states with atomic and
molecular targets. In this presentation we compare those results with calculations being conducted at several institutions. For this presentation we will focus on electron emission
from neon following interactions with carbon
ions with energies from 0.067 MeV/u to 0.35
MeV/u and incident charge states from C+ to
C3+ . Electron energies from 10 to 1500 eV are
observed at emission angles from 20 to 120 degrees. The calculations separate the process
into ionization of the target by the screened incident nucleus and the ionization of the target
by the screened target nucleus. By summing
these components in the rest frame of the target we can compare to the measured electron
spectra. Figure 1 shows the single differential cross sections for ejection of electrons in
C+ -Ne collisions. Note the small contribution
from ionization of the projectile. As the energy increases the contribution from projectile
ionization increases; likewise as the ion energy
decreases that contribution decreases. The excellent agreement shown in Figure 1 provides
confidence to our use of Bohr theory for this energy range for this target. Doubly -differential
cross sections based on the Classical Trajectory Monte Carlo (CTMC) techniques are compared with measurements in Fig. 2 for electron
emission at 30 degrees. Again, excellent agreement has been observed. We are currently exploring different incident charge states and will
present those data at the meeting along with
available theory.
Figure 1. Single differential cross sections for 2.4
MeV C+ on Neon. The lines are results of a Bohr
calculations and the open symbols are measured
cross sections.
Figure 2. Doubly differential cross section for ionization of neon by 2.4 MeV C+ ions. Lines are calculated with CTMC and the open symbols are from
measurements.
Acknowledgements: One of us (KT) was supported
by the grant Bolyai from the Hungarian Academy
of Sciences and the Hungarian National Office for
Research and Technology.
a) East Carolina University, Department of Physics,
Greenville, NC 27858, USA
b) Department of Physics and Chemistry, University
of Southern Denmark, 5230 Odense M, Denmark
c) Institut für Experimentalphysik, Johannes-KeplerUniversität, 4040 Linz-Auhof, Austria
d) Physics Division, Oak Ridge National Laboratory,
Oak Ridge, TN 37831-6373, USA
10