\begin{table}%t2
\caption{Model parameters.}\label{par}
%\centering
\par
\begin{tabular}{lcc}
\hline
\hline
Parameter                     & Diffuse Phase & Dense Phase \\
\hline
$n_{\rm H}$ (cm$^{-3}$)       & 100     & 20000   \\
$\chi$                        & 2.0     & 0.5     \\
$\zeta$ (10$^{-17}$ s$^{-1}$) & 25      & 25      \\
$T$(K)                          & 60      & 20      \\
$N$(H$_{2}$) (cm$^{-2}$)      & 4.5(20) &         \\
$N$(C$_{2}$) (cm$^{-2}$)      &         & 1.9(13) \\
\hline
\end{tabular}
\end{table}