\begin{table}%t1
\caption{\label{tab1}Observed transition frequencies for CH$_2$D$^+$ (in MHz).}
\small%\centering
\par
\begin{tabular}{ccr@{}lr@{}l}
\hline\hline\noalign{\smallskip}
\multicolumn{2}{c}{Transition} &\multicolumn{2}{c}{This work\tablefootmark{a}} &\multicolumn{2}{c}{\cite{rosslein:ch2d+}\tablefootmark{b}}  \\
\hline
  $2_{12}{-}1_{11}$ &~~ $o$  &~~ 490~012.&247(30)   &   490~012.&30        \\
  $2_{11}{-}1_{10}$ &~~ $o$  &~~ 624~492.&648(20)   &   624~492.&58        \\
  $3_{13}{-}2_{12}$ &~~ $o$  &~~ 722~354.&622(25)   &   722~354.&74\tablefootmark{c}    \\
  $3_{22}{-}2_{21}$ &~~ $p$  &~~ 835~464.&376(50)   &   835~465.&29\tablefootmark{c}    \\
\hline
\end{tabular}
\tablefoot{\tablefoottext{a}{The numbers in parentheses indicate estimated uncertainties to the last significant digits.}  \\
\tablefoottext{b}{The uncertainties of these predicted values is given  to be $2\times 10^{-5}$. It translates to~12~MHz uncertainty  for the 624.5~GHz line.}   \\
\tablefoottext{c}{Calculated value obtained by using the molecular  constants given by \cite{rosslein:ch2d+}.}} \vspace{-3mm}
\end{table}