\begin{table}%t1
\caption{\label{t:qcc-theor}Computed quadrupole-coupling constants $eQq$ (kHz) for \dcop,
HN\thc, and DNC$^{a}$.} 
%\centerline
{
\par
\begin{tabular}{lcccl}
\hline \hline
Computational level    & \multicolumn{1}{c}{\dcop} & \multicolumn{1}{c}{HN\thc} & \multicolumn{2}{c}{DNC} \\
\hline
                       & D     & N     & D     & \multicolumn{1}{c}{N} \\
\hline
CCSD/cc-pCVDZ          &       &       & 308.6 & 1009.5  \\
CCSD(T)/cc-pCVDZ       &       &       & 309.3 & 1021.4 \\
CCSDT/cc-pCVDZ         &       &       & 309.3 & 1029.1 \\ 
CCSDTQ/cc-pCVDZ        &       &       & 309.2 & 1033.2 \\
CCSD(T)/cc-pCVTZ       &       &       & 290.8 &  431.9 \\
CCSD(T)/cc-pCVQZ       & 159.2 & 341.6 & 279.8 &  341.6 \\
CCSD(T)/cc-pCVQZ + vib & 153.6 & 294.8 & 259.1 &  325.2 \\
CCSD(T)/cc-pCV5Z       & 162.2 & 325.5 & 278.3 &  325.5 \\
CCSD(T)/cc-pCV5Z + vib & 156.0 & 279.5 & 257.6 &  309.6 \\     
\hline
\end{tabular}}
\medskip
\par
$^a$ All calculations have been performed at geometries obtained at the
same computational level.
\end{table}