\begin{table}%t1
\caption{Adopted gas-phase elemental abundances with respect to \mbox{hydrogen}.}
\label{abuntab}
%\centering
\par
\begin{tabular}{l l}
\hline  \hline
Element & Abundance\\
\hline
D & $1.5\times 10^{-5}$\\
He & $7.5\times 10^{-2}$\\
C & $7.9\times 10^{-5}$\\
N & $2.6\times 10^{-5}$\\
O & $1.8\times 10^{-4}$\\
S & $1.7\times 10^{-6}$\\
PAH & $1.0\times 10^{-7}$\\
\hline
\end{tabular}
\end{table}