\begin{table}%t1
\caption{\label{T1}Initial fractional abundances with respect to total hydrogen nuclei.}
%\centering
\small
\begin{tabular}{lc|lc} 
\hline \hline
 Species & {\rm Abundance} & Species & {\rm Abundance} \\
 \hline
&&& \\[-8pt]
 H$^+$ & $1.0\times 10^{-11}$ & CO & $1.3\times 10^{-4}$ \\
 He$^+$ & $2.5\times 10^{-12}$ & CO$_2$ & $3.0\times 10^{-6}$ \\
 H$_3^+$ & $1.0\times 10^{-9}$ & H$_2$CO & $2.0\times 10^{-6}$ \\
 Fe$^+$ & $2.4\times 10^{-8}$ & CH$_3$OH & $2.0\times 10^{-7}$ \\
 He & $1.0\times 10^{-1}$ & C$_2$H$_5$OH & $5.0\times 10^{-9}$ \\
 S & $5.0\times 10^{-9}$ & O$_2$ & $1.0\times 10^{-6}$ \\
 Si & $3.6\times 10^{-8}$ & H$_2$O & $2.8\times 10^{-4}$ \\
 C$_2$H$_2$ & $5.0\times 10^{-7}$ & N$_2$ & $3.7\times 10^{-5}$ \\
 CH$_4$ & $2.0\times 10^{-7}$ & NH$_3$ & $6.0\times 10^{-7}$ \\
 C$_2$H$_4$ & $5.0\times 10^{-9}$ & H$_2$S & $1.0\times 10^{-7}$ \\
 C$_2$H$_6$ & $5.0\times 10^{-9}$ & OCS & $5.0\times 10^{-8}$ \\ 
 \hline
\end{tabular}
\end{table}