\begin{table}%t6
\caption{\label{CCH_parameters}Spectroscopic parameters$^a$ (MHz) of C$_2$H in comparison to previous values.}
%\centerline
 {
\begin{tabular}{l r@{}l r@{}l}
\hline\hline
Parameter & \multicolumn{2}{c}{present value} & \multicolumn{2}{c}{M{\"u}ller et~al. (\cite{Muller00})} \\
\hline
$B$                     & 43~674&.5177~(13) & 43~674&.5289~(12)  \\
$D \times 10^3$         &   105&.515~(53)  &   105&.687~(51)   \\
$H \times 10^6$         &  $-$0&.42~(32)   &     0&.32~(32)    \\
$\gamma$                & $-$62&.6103~(45) & $-$62&.6029~(43)  \\
$\gamma ^D \times 10^3$ &  $-$2&.227~(250) &  $-$2&.313~(255)  \\
$b_F$                   &    44&.4788~(82) &    44&.4922~(183) \\ 
$b_F^D$                 &      &$-$         &  $-$0&.0100~(38)  \\
$c$                     &    12&.2389~(232)&    12&.2256~(261) \\
$C$                     &  $-$0&.0087~(53) &      &$-$          \\
\hline
\end{tabular}}
\par
\smallskip
$^a$ Numbers in parentheses are one standard deviation in units of the least significant figures. 
\end{table}