\begin{table}%T9
\caption{\label{D/Ho}Deuterium fractionation of several molecular species.} 
\small%\centerline
{
\begin{tabular}{lcccc}
\hline\hline\noalign{\smallskip}
Source & $\rm\frac{N_2D^+}{N_2H^+}~^1$ & $\rm\frac{NH_2D}{NH_3}~^2$ & $\rm\frac{DCO^+}{HCO^+}~^3$ & $\rm\frac{D_2CO}{H_2CO}~^4$ \\
\noalign{\smallskip}\hline 
L1448~IRS~3 & 0.081 & 0.17 & -- & --\\ 
L1448~C & 0.104 & 0.20 & 0.011 & 0.24\\
IRAS~03282 & 0.219 & 0.22 & -- & --\\
HH 211 & 0.271 & 0.33 & -- & --\\
Barnard 5 & 0.034 & 0.18 & -- & --\\
L 1527 & $<$ 0.034 & -- & 0.048 & 0.44 \\
L 483 & 0.057 & -- & 0.006 & --\\
L 723 & 0.045 & -- & 0.004 & --\\
L 1157 & 0.045 & -- & 0.016 & $\leq$$0.08$\\  
\hline
\end{tabular}}
\smallskip 
$^1$ This work; $^2$ Hatchell~(\cite{nh3}); $^3$ J\o rgensen et~al.~(\cite{jor}); $^4$ Parise et~al.~(\cite{d2co}).
\end{table}