\begin{table}%[h]

\caption{Initial gas-phase and total abundances.}\label{tel}
%\centerline
{
\begin{tabular}{lccr} \hline\hline
Species & $x(i)$ $T > 100$~K & $x(i)$ $T < 100$~K & $x(i)$ total \\ \hline
CO         & 1.8E--04$^a$ & 1.8E--04$^a$ &         \\ 
CO$_2$     & 1.5E--05$^b$ & 0.00$^f$    &         \\ 
H$_2$O     & 7.5E--05$^c$ & 0.00$^f$    &         \\
H$_2$S     & 8.0E--07$^d$ & 0.00$^f$    &         \\
N$_2$      & 3.5E--05$^e$ & 3.5E--05$^e$ &         \\
CH$_4$     & 5.0E--08$^e$ & 5.0E--08$^e$ &         \\
C$_2$H$_4$ & 4.0E--08$^e$ & 4.0E--08$^e$ &         \\
C$_2$H$_6$ & 5.0E--09$^e$ & 5.0E--09$^e$ &         \\
H$_2$CO    & 6.0E--08$^e$ & 0.00$^f$    &         \\
CH$_3$OH   & 5.0E--07$^e$ & 0.00$^f$    &         \\
He         & 8.5E--02$^h$ & 8.5E--02$^h$  & 8.5E--02$^h$ \\
C          & 1.0E--08$^h$  & 1.0E--08$^h$  & 3.5E--04$^i$ \\
N          & 1.0E--08$^h$  & 1.0E--08$^h$  & 1.1E--04$^i$ \\
O          & 0.00$^e$    & 4.0E--05$^g$ & 4.5E--04$^i$ \\
S          & 0.00$^e$    & 3.0E--09$^d$ & 1.0E--05$^i$ \\
Si         & 1.0E--08$^h$  & 1.0E--08$^h$  & 3.5E--05$^i$ \\
Cl         & 1.0E--08$^h$  & 1.0E--08$^h$  & 9.3E--08$^i$ \\
Fe         & 1.0E--08$^e$ & 1.0E--08$^e$ & 3.2E--05$^i$ \\
Ne         & 1.0E--08$^h$  & 1.0E--08$^h$  & 1.4E--04$^i$ \\
Na         & 1.0E--08$^h$  & 1.0E--08$^h$  & 2.1E--06$^i$ \\
Mg         & 1.0E--08$^h$  & 1.0E--08$^h$  & 4.0E--05$^i$ \\
Al         & 1.0E--08$^h$  & 1.0E--08$^h$  & 3.1E--06$^i$ \\
Ar         & 1.0E--08$^h$  & 1.0E--08$^h$  & 3.8E--06$^i$ \\
Ca         & 1.0E--08$^h$  & 1.0E--08$^h$  & 2.3E--06$^i$ \\
Cr         & 1.0E--08$^h$  & 1.0E--08$^h$  & 5.0E--07$^i$ \\
Ni         & 1.0E--08$^h$  & 1.0E--08$^h$  & 1.8E--06$^i$ \\ \hline
\end{tabular}}
\medskip 
All abundances are relative to total hydrogen. Only 
the abundances in the $2.$ and $3.$ column enter the chemistry. 
The total abundances $x(i)$ ($4.$ column) are for the attenuation 
of the X-rays.
\\
$^a$ van der Tak et~al. ($1999$), $^b$ Boonman et~al. ($2003$b), 
$^c$ Boonman \& van Dishoeck ($2003$), $^d$ see text, $^e$ Charnley ($1997$), 
$^f$ assumed to be frozen-out or absent in cold gas-phase, $^g$ taken to be $\sim$ 
consistent with Meyer et~al. ($1998$), $^h$ assumed abundances, $^i$ Yan ($1997$).
\end{table}