\begin{table}%t4
\caption{\label{table_selection_rules}Selection rules for the ro-vibration transitions in addition to $\Delta J = 0,\ \pm1$. The transitions in brackets are weaker than the main transitions. For ro-vibrational transitions, the parity of $K_a+K_c+v_3$ has to be
  conserved. Transitions of type a only occur for oblate molecules,
  whereas transitions of type c are only found for prolate molecules.
  Both oblate and prolate molecules can have b-type transitions.}
  %\centering
\par
\begin{tabular}{llll}
 \hline\hline
 \multicolumn{1}{c}{Transition}&\multicolumn{1}{c}{Criterion} & \multicolumn{1}{c}{$\Delta K_{{a}}$}& \multicolumn{1}{c}{$\Delta K_{{c}}$}\\
 \hline
 $a$-type & $\mu_a \neq 0$ & \phantom{$\pm$}$0, \pm 2\ (\pm 4,\ ...)$    & $\pm 1\ (\pm 3,\pm 5,\ ...)$ \\
 $b$-type & $\mu_b \neq 0$ & $\pm 1, \pm 3\ ( \pm 5,\  ...)$   & $\pm 1, \pm 3\ ( \pm 5,\  ...)$\\
 $c$-type & $\mu_c \neq 0$ & $\pm 1\ (\pm 3,\pm 5,\ ...)$ & \phantom{$\pm$}$0, \pm 2\ (\pm 4,\ ...)$ \\
 \hline
\end{tabular}  
\end{table}