\begin{table}%t2
\caption{\label{parameter}Spectroscopic parameters$^a$ (MHz) of CO in excited vibrational states compared with that in the ground vibrational state.}
\small%\centerline
 {
\begin{tabular}{rcccc}
\hline \hline
%&&&& \\[-8pt]
Parameter & \multicolumn{1}{c}{$\varv = 0^b$} & \multicolumn{1}{c}{$\varv = 1$} & \multicolumn{1}{c}{$\varv = 2$} & \multicolumn{1}{c}{$\varv = 3$} \\
\hline
$B_{\varv}$             & 57~635.968~019~(28) & 57~111.243~12~(66) & 56~586.555~00~(157) & 56~061.910~5~(59) \\
$D_{\varv} \times 10^3$ &     183.504~89~(16)  &     183.490~3~(71)  &     183.474~0~(234)  &     183.511~(63)    \\
$H_{\varv} \times 10^9$ &     171.68~(10)       &     177.9~(145)      &     163.~(53)         &     241.~(134)      \\
\hline
\end{tabular}}
\medskip
$^a$ Numbers in parentheses are one standard deviation in units of the least significant figures.\\
$^b$ \citet{CO_v0_rot_1997}.
\end{table}