\begin{table}%t9
%\centering
\par
\caption {\label{LVG}H$_2$ volume densities and molecular column densities of 
H$^{13}$CO$^+$ and HN$^{13}$C derived assuming extended emission for both 
the ambient and the precursor components of L1448-mm.
}
\begin{tabular}{lcccc}
\hline \hline
\noalign{\smallskip}
& \multicolumn{2}{c} { H$_2$ density (cm$^{-3}$)}&\multicolumn{2}{c} { Column density (cm$^{-2}$)} \\ \cline{2-3} \cline{4-5}
 Molecule & Ambient & Precursor & Ambient & Precursor\\
\hline
\multicolumn{5}{c}{(0,~20)}\\ 
H$^{13}$CO$^+$   &   $1.4\times10^5$   & $3.5\times10^5$   &$4.8\times10^{11}$  & $4.0\times10^{11}$  \\
HN$^{13}$C   & $\la$$ 1.9\times10^5$    &  $\la$$ 9.2\times10^5$  &  $\la $$6.4\times10^{11}$  & $\la $$1.5\times10^{11}$ \\ \hline
\multicolumn{5}{c}{(20,~0)}\\
H$^{13}$CO+   & $\la $$8.8\times10^4$ &  $1.8\times10^5$    & $\la $$5.1\times10^{11}$    &  $4.3\times10^{11}$  \\
HN$^{13}$C   & $\la $$1.8\times 10^5$ & $\la$$ 3.3\times10^5$  &  $\la$$ 7.2\times10^{11}$   &  $\la$$ 4.1\times10^{11}$ \\ \hline
\multicolumn{5}{c}{(--20,~0)}\\ 
H$^{13}$CO$^+$    &  $\la $$8.7\times10^4$     & $7.1\times 10^4$ & $\la$$ 3.5\times10^{11}$   & $6.4\times10^{11}$\\
HN$^{13}$C   &   $1.2\times10^5$  & $\la$$ 6.1\times10^5$    & $1.4\times10^{12}$   & $\la$$ 2.0\times10^{11}$ \\ \hline
\par
\end{tabular}
\par
\end{table}