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"Transparency" in atom - metal cluster collisions
The energy loss ΔE in Na9+ + Na collisions as a function
of the c.m. bombarding energy Ec.m. clearly shows a minimum at intermediate
Ec.m. around 1 keV. Obviously, the corresponding impact velocity is too large to
excite vibrations and still too small to excite electrons and, thus, the atom penetrates
the cluster nearly freely ("Transparency") [1].
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Total kinetic energy loss of relative motion ΔE in central Na9+ + Na
collisions for a fixed collision geometry (see inset) as a function of the center-of-mass impact
energy Ecm calculated with NA-QMD (solid line) and QMD (dotted line). Vibrational and
electronic contributions to ΔE are distinguished by gray and light-gray shaded areas,
respectively. (Fig. taken from [1])
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The transparency effect results in a plateau of the fragmentation cross section
σfrag as a function of Ec.m..
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Total fragmentation cross sections as a function of Ecm calculated with NA-QMD (solid line).
The circles are experimental data. (Fig. taken from [1])
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U. Saalmann and R. Schmidt,
Excitation and Relaxation in Atom-Cluster Collisions,
Phys. Rev. Lett. 80, 3213 (1998).
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