3.6
Accelerating multiple scattering of the emitted electrons in collisions of ions
with atoms and molecules
T. Ricsóka, Gy. Vı́kor a) , Sz. Nagy a) , K. Tőkési, Z. Berényi, B. Paripás b) , N. Stolterfoht c)
and B. Sulik
Ionization is one of the fundamental phenomena studied in atomic collision physics.
Double differential spectra of electrons ejected
in ion-atom and ion-solid collisions provide detailed information about the ionization dynamics. During the past decade special emphasis have been laid on the emission of the
fast electrons in collisions of heavy partners
[1]. Significantly enhanced emission of fast
electrons above the binary encounter energy
was observed in both ion-atom [2] and ion-solid
collisions [3]. In some cases, the fast electrons
have been identified as originated from double [4] or multiple [2] scattering by the projectile and target cores. Since the moving projectile ion is much heavier than the electron, such
kind of multiple scattering of the electron also
accelerates it. The process is often denoted as
Fermi-shuttle acceleration [1].
In the present work, we measured the double differential cross-sections for electron emission in collisions of 700–1500 keV N + ions with
N2 , Ne and Ar targets. We studied the target
atomic number (ZT ) dependence of the yield
of the Fermi-shuttle type triple and quadruple
scattering in these collisions.
We performed classical trajectory MonteCarlo calculations for the target ionization.
Figure 1 compares the present experimental
double differential cross sections with the results of the CTMC calculation for electron
emission at 30◦ , 90◦ and 150◦ in 0.75 MeV N +
+ Ar collisions as a function of the ejected electron energy. The experimental double differential cross-sections are in good agreement with
the theoretical values, and all the expected target ionization structures (P, P-T, P-T-P and
P-T-P-T) clearly appear in the spectra.
We consider the present work as a starting
point of a systematic study, a combined experimental and CTMC analysis of a wide range of
collision systems.
Figure 1. Experimental double differential cross
section in comparison with theoretical CTMC results for electron emission at 30◦ , 90◦ and 150◦ in
0.75 MeV N + + Ar collisions as a function of the
ejected electron energy.
Acknowledgements
This work was supported by Hungarian
OTKA Grants (T046905, M27839) and by the
Hungarian-Swedish KVA-collaboration.
a) Department of Atomic Physics, Stockholm University, 10405 Sweden
b) Department of Physics, University of Miskolc, 3515
Miskolc-Egyetemváros, Hungary
c) Hahn-Meitner Institute Berlin, D-14109 Berlin,
Germany
[1] B. Sulik, N. Stolterfoht, R. Hellhammer, Z. Pesic,
Cs. Koncz, K. Tokési, D. Berényi, Nucl. Inst.
and Meth. B 212 (2003) 32.
[2] B. Sulik, Cs. Koncz, K. Tokési, A. Orbán, D.
Berényi, Phys. Rev. Lett. 88 (2002) 073201.
[3] R. A. Baragiola, E. V. Alonso, A. Oliva, A. Bonnano, F. Xu, Phys. Rev. A 45 (1992) 5286.
[4] S. Suárez, R. O. Barrachina, and W. Meckbach,
Phys. Rev. Lett. 77 (1996) 474.
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