\begin{table}%T5
\par
\caption{\label{tab:gas}A comparison of steady-state molecular~D/H ratios from gas-phase models. $T=10$~K, $n$(H$_2)=10^4$~cm$^{-3}$.}
%\centerline
{
\begin{tabular}{lcc}
\hline\hline
 & \rosu\ & \rneufneuf \\
\hline
HD/H$_2$            & 2.8($-$5) & 2.7($-$5)  \\ 
D$_2$/H$_2$         & 7.2($-$7) & 7.6($-$7)  \\ 
H$_2$D$^+$/H$_3^+$  & 1.1($-$1) & 1.1($-$1)\\ 
HD$_2^+$/H$_3^+$    & 6.8($-$3) & 7.8($-$3)  \\ 
D$_3^+$/H$_3^+$     & 3.9($-$4) & 4.8($-$4) \\ 
N$_2$D$^+$/N$_2$H$^+$ & 4.2($-$2) & 4.6($-$2)\\ 
DCO$^+$/HCO$^+$     & 5.0($-$2) & 5.2($-$2)\\ 
DCS$^+$/HCS$^+$     & 1.3($-$2) & 3.5($-$2)\\ 
D/H                 & 1.2($-$2) & 1.3($-$2) \\ 
ND/NH               & 4.7($-$2) & 5.3($-$2) \\
NH$_2$D/NH$_3$      & 3.1($-$2) & 2.5($-$2)   \\ 
NHD$_2$/NH$_3$      & 3.2($-$4) & 2.5($-$4)   \\ 
ND$_3$/NH$_3$       & 1.4($-$6) & 9.7($-$7)   \\ 
DCN/HCN             & 2.1($-$2) & 2.0($-$2)   \\ 
DNC/HNC             & 1.5($-$2) & 1.8($-$2)  \\ 
HDCO/H$_2$CO        & 4.0($-$2) & 4.2($-$2)   \\ 
D$_2$CO/H$_2$CO     & 3.9($-$4) & 4.3($-$4)   \\ 
OD/OH               & 4.7($-$2) & 6.3($-$2)   \\ 
HDO/H$_2$O          & 2.3($-$2) & 2.3($-$2)   \\ 
D$_2$O/H$_2$O       & 7.1($-$5) & 7.2($-$5)   \\ 
CH$_3$OD/CH$_3$OH   & 2.5($-$2) & 2.9($-$2)   \\ 
CH$_2$DOH/CH$_3$OH  & 9.2($-$2) & 9.3($-$2) \\ 
CH$_2$DOD/CH$_3$OH  & 1.8($-$3) & 2.3($-$3)  \\ 
CHD$_2$OH/CH$_3$OH  & 3.8($-$3) & 4.0($-$3)  \\ 
CHD$_2$OD/CH$_3$OH  & 6.9($-$5) & 9.3($-$5)  \\ 
CD$_3$OH/CH$_3$OH   & 9.1($-$5) & 9.3($-$5)  \\ 
CD$_3$OD/CH$_3$OH   & 1.5($-$6) & 2.1($-$6) \\ 
HDCS/H$_2$CS        & 4.5($-$2) & 4.4($-$2)  \\ 
D$_2$CS/H$_2$CS     & 4.5($-$4) & 4.3($-$4)  \\ 
HDS/H$_2$S          & 3.9($-$2) & 3.3($-$2)  \\ 
D$_2$S/H$_2$S       & 2.1($-$4) & 8.5($-$5)  \\ 
 \hline
\end{tabular}}
\smallskip
Note: $a(-b)$ implies $a\times10^{-b}$.
\end{table}