\begin{table}%t1
        \caption{Summary of adopted dipole moments$^{a,b}$.      }
 \label{tab_dipole} 
   \begin{tabular}{lcccc}    
    \hline\hline
   % \noalign{\smallskip}
    \multicolumn{1}{c}{  {\rm Molecule  $^{\it a}$ }} & 
            \multicolumn{1}{c}{$\mu_0$} &
    \multicolumn{1}{c}{$\mu_{\rm e}$} &
    \multicolumn{1}{c}{\rm {Method}} &
    \multicolumn{1}{c}{\rm {reference}} 
    %&
     \\
             &
             \multicolumn{1}{c}{\rm {[D]}} & 
    \multicolumn{1}{c}{\rm {[D]}} &
            & 
                        \\
    \noalign{\smallskip}
            \hline
 CO & 0.110 & & {\rm {expt.}} & 1 \\
 SO & $1.52\pm .02$ & & {\rm {expt.}} & 2  \\
SO$_2$ & 1.633 & & {\rm {expt.}} &  3 \\
CS &  $1.958\pm .005$ & & {\rm {expt.}} &  4\\
SiO &  3.098 & &{\rm {expt.}} &  5 \\
SiS & $1.73\pm .06$ & & {\rm {expt.}} & 6 \\
 HCO$^+$ & $-3.93\pm .01$ & $-3.90\pm .01$ & {\rm ab~initio} & 7  \\
 HOC$^+$ & 2.74 &  2.8 & {\rm ab~initio} & 8, 9  \\
 OCS &  0.7152 & & {\rm {expt.}} & 10  \\
HC$_3$N & 3.732 && {\rm {expt.}} & 11 \\
 HCN & 2.985 && {\rm {expt.}} & 12 \\
 HNC & $3.05\pm .1$ && {\rm {expt.}} & 13\\
 HNCO & 1.602 && {\rm {expt.}} & 14\\
 c-C$_3$H$_2$ & $3.27\pm .01$ & & {\rm {expt.}} & 1 \\
CH$_3$CN & 3.922 & & {\rm {expt.}}  &  15 \\
H$_2$CO &  2.332 & &{\rm {expt.}} & 16 \\
 N$_2$H$^+$ & &3.4 &{\rm ab~initio} &  17\\
HCS$^+$ & 1.958  & & {\rm ab~initio} &  18\\
CH$_3$OH &  0.896 & & {\rm {expt.}} & 19 \\
NH$_3$ & $1.476\pm .002$ & & {\rm {expt.}} &  20 \\
H$_2$O & 1.847 & & {\rm {expt.}} &  21 \\
SiC$_2$ & $2.393\pm .006$ & & {\rm {expt.}} &  22  \\ 
HCl & 1.109 & & {\rm {expt.}} &  23  \\ 
OH & 1.655 & & {\rm {expt.}} &  24 \\ 
 H$_3$O$^{+}$ & 1.44 &&  {\rm ab~initio}  &  25  \\ 
 \hline
 \end{tabular}
          \smallskip
 \noindent 
 $^{a}$ Same data are also adopted for isotopes and deuterated
 species,\protect unless stated in the datafile. 
\par
  \noindent 
 $^{b}$ All values are in units of
debye (D), where 1 D = $10^{-18}$~esu~cm. When the original source has
presented $\mu$ in atomic units, a conversion factor of 1 au = $ea_0$ =
2.54175 D has been applied.
\par
 \noindent
 Refs. -- (1) \citet{Goorvitch94}; (2) \citet{Lovas92}; (3) \citet{Patel79}; (4) \citet{Winnewisser68};
 (5) \citet{Raymonda70}; (6) \citet{Hoeft69}; (7) \citet{Botschwina93}; (8) \citet{Botschwina89};
 (9) \citet{DeFrees82}; (10) \citet{Muenter68}; (11) \citet{DeLeon85}; (12) \citet{Ebenstein84};
 (13) \citet{Blackman76}; (14) \citet{Hocking75};  (15) \citet{Gadhi95}; (16) \citet{Fabricant77}; (17) \citet{Green74b};
 (18) \citet{Botschwina85}; (19) \citet{Sastry81}; (20) \citet{Cohen74}; (21) From JPL based on \citet{Camy-Peyret85}; 
 (22) \citet{Suenram89}; (23) \citet{DeLeeuw71};  (24) \citet{Peterson84}; 
  (25) \citet{Botschwina84}.
\end{table}