\begin{table}%t6
\caption{\label{t:hnc-13}Hyperfine parameters$^a$ (kHz) of HN\thc\ in comparison to ab initio values.}
%\centerline
{
\begin{tabular}{lr@{}lr@{}l}
\hline
\hline
Parameter   & \multicolumn{4}{c}{Value} \\
\cline{2-5}
            & \multicolumn{2}{c}{experimental} & \multicolumn{2}{c}{ab initio} \\
\hline
$eQq$(N)     & +272&.5~(51) & +279&.5  \\
$C_I$(N)     &   +6&.33$^b$ &   +6&.33 \\
$C_I$(\thc)&  +23&.46$^b$ &  +23&.46 \\
$C_I$(H)     & $-$4&.49$^b$ & $-$4&.49 \\
$S$(HN)      & $-$8&.79$^b$ &     &$-$ \\
$S$(N\thc) & $-$1&.37$^b$ &     &$-$ \\
$S$(H\thc) & $-$2&.98$^b$ &     &$-$ \\
\hline
\end{tabular}}
\medskip
\par
$^a$ Numbers in parentheses are one standard deviation in units 
of the least significant figures.\\
$^b$ Kept fixed to computed values in the analysis.
\end{table}