\title{\normalsize
ANORMALOUSLY ENHANCED SCREENING POTENTIAL OBSERVED\\
IN COLLISIONS OF NOBLE GAS IONS ON CARBON ATOMS IN $C_{60}$\\
\vspace{20pt}
I. Arai$^{\ast}$, T. Miura$^{\ast}$, M. Imanaka$^{\ast}$, H. Sasaki$^{\ast}$,
S. Tomita$^{\sharp}$ and S.M. Lee$^{\ast}$\\
\vspace{20pt}
$^{\ast}$Institute of Physics, University of Tsukuba, Ibaraki 305, Japan\\
$^{\sharp}$CEA Grenoble, Service des Ions, Atomes et Agregates,
17 rue des Martyrs 38054,\\
Grenoble Cedex 9, France\\
\vspace{10pt}
\begin{quote}
Collision dynamics of noble gas ions $He^{+}$, $Ne^{+}$, $Ar^{+}$ and
$Xe^{+}$ on carbon atoms in $C_{60}$ at incident energies from $3.2 keV$
to $9.8 keV$ has been studied. Measured cross sections have shown anormalously
enhanced screening which  could not be accounted for by well-known
Moli\{e}re's potential. Effective potentials have been evaluated so as to
fit the cross sections. Extra screening factors are found to be Wood-Saxon
type functions. Substantially new interaction mechanism is suggested.
\end{quote}
}

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