\begin{table}%t1 
\caption{\label{table:srim}SRIM input parameters for graphite and a-C:H.}          
\par
\small%\centerline
 {
\begin{tabular}{l c c c c c}         
\hline\hline                    
&&&&& \\[-8pt]
Material & $\rho \rm(g~cm^{-3})$ & $X_{\rm H}$ & $U_{\rm 0}\rm (eV)$ &
$E_{\rm D} (\rm eV)$ & $E_{\rm L} (\rm eV)$ \\     
\hline                         
``old graphite'' & -- & 0 & 3 & 11 & 2 \\     
graphite & 2.26 & 0 & 7.4 & 28 & 3    \\
a-C:H$_{(1)}$ & 1.5 & 0.2 & 4 & 10 & 3 \\
a-C:H$_{(2)}$ & 1.4 & 0.4  & 4 & 10 & 3 \\
a-C:H$_{(3)}$ & 1.3 & 0.55  & 4 & 10 & 3 \\
\hline                                    
\end{tabular}}
\medskip
Notes.  $\rho$ is the bulk material density (taken from \citealt{smith84} for \mbox{a-C:H}), $X_{\rm H}$ the hydrogen atomic fraction, $U_0$~is the surface atom binding energy, $E_{\rm D}$~bulk atom displacement energy and $E_{\rm L}$ the lattice energy. The values used by \cite{jurac98} are here designated as ``old graphite''.
\end{table}