\begin{table}%t6
%\centering
\par
\caption {\label{tab:Nthick}Species masses in the disk and emission line characteristics.
  A velocity width of $\Delta v_D\!=\!1$~km~s$^{-1}$ is assumed.}
\begin{tabular}{cccccc}
\hline\hline
 & $\rm\!\!\!\!\!Mass~[M_{\displaystyle\oplus}]\!\!\!\!\!\!$& Type 
                        & $\lambda\rm~[\mu m]$  
                        & $N_{\rm thick}\rm~[cm^{-2}]$ 
                        & $E_u\rm~[K]$\\
\hline
%&&\\[-2.2ex]
C{\sc ii}          & 0.055   & fine-struc.  & $158$      
                        & $2\times 10^{17}$   & 91    \\ 
C{\sc i}           & 0.079   & fine-struc.  & $370$     
                        & $2\times 10^{17}$   & 62    \\
O{\sc i}           & 4.6     & fine-struc.  & $63$    
                        & $3\times 10^{17}$   & 230   \\
CO                 & 4.2     & rotational   & $400{-}2600$ 
                        & $\sim$$10^{15}$      & $\sim$$5{-}300$ \\
                   &         & $\!\!$ro-vib. fund.$\!\!$& $4.6$
                        & $\sim$$10^{15}$      & $\sim$$3100$ \\
$\!\!\!\!$H$_2$O$\!\!$ & 0.007  & rotational   & $50{-}300$
                 & $\sim$$10^{13}-10^{15}$ & $\sim$$60{-}1000$ \\ 
H$_2$              & 2540    & $\!\!$ro-vib.$\!\!$   & $2{-}28$     
      & $\sim$$10^{23}-10^{24}$ & $\sim$$500{-}8000$ \\
$\!\!\!\!$MgII$\!\!$ & 0.15  & resonance k  & $0.28$   
                        & $6\times 10^{11}$   & 51~300 \\
\hline
\end{tabular}
\end{table}