\begin{table}%t1
\par
\renewcommand{\arraycolsep}{1.1}
\caption {\label{far_IR}Far-IR rovibrational bands of PAH cations adopted in this work, with the percentage of the total oscillator strength in each band.}
%\centerline
 {
\begin{tabular}{cccccc}
\hline
\hline
$\lambda_{\rm cations}$$^a$ & $\nu_{\rm cations}$ & $\Delta \nu$ & $\sigma_{i}/N_{\rm C}$  & $\%$  & Type$^b$ \\
($\mu$m)            & (cm$^{-1}$)     & (cm$^{-1}$)  & $(\rm{10^{-20}~cm^{2}})$ & (cations)        \\
\hline
30.2                & 331             & 300          & $9.6\times 10^{-3}$       & 69.5      & 2/3 ip   \\
                      &                    &                 &                                      &              & 1/3 op \\
74.1                & 135             & 100          & $9.9\times 10^{-3}$       & 23.9      & 2/3 ip \\
                      &                    &                 &                                      &              & 1/3 op \\
$4.9\times N_{\rm C}$   & 2040/${N_{\rm C}}$  & 100          & $2.7\times 10^{-3}$       & 6.6       & 2/3 ip \\
                      &                    &                 &                                      &              & 1/3 op \\
\hline
\end{tabular}}
\par
\smallskip
$^a$  {Similar bands were obtained for PAH neutrals.}
$^b$  {In-plane (ip) or out-of-plane (op) character of the band.}
\end{table}