\begin{table}%T3
\caption{\label{t3}$I_{6-10~\mu {\rm m}}/I_{10-15~\mu {\rm m}}$ ratios ($R$) for the ground states of PAH$^+$ and their complexes with Si and the effects of the complexation on this ratio.}
%\centerline
 {
\begin{tabular}{ccccccc}
\hline \hline  \\[-3mm]
 & & $R$(SiPAH$^+$)/ & & $\delta$$\lambda$ oop C--H bend$^*$ & &  $\delta$$\lambda$ ip C--C stretch$^*$\\
 & $R$ & $R$(PAH$^+$) & $\lambda$ oop C--H bend & SiPAH$^+$ vs. PAH$^+$ &  $\lambda$ ip C--C stretch$^*$ & SiPAH$^+$ vs. PAH$^+$$^*$\\
\hline
\noalign{\smallskip}
C$_{10}$H$_8$$^+$ & 2.92 & & 13.28 & & 6.60 (6.55) & \\
$[$SiC$_{10}$H$_8]^+$ & 0.97 & 0.33 & 13.19 & --0.09 & 6.43 & --0.17\\ 
 & & & 12.02 & new & & \\
C$_{16}$H$_{10}$$^+$ & 2.86 & & 11.46 & & 6.47 & \\
$[$SiC$_{16}$H$_{10}]$$^+$ (1) & 3.56 & 1.24 & 11.68 & +0.22 & 6.22 & --0.25\\ 
 & & & 11.15 & --0.31; new & & \\
$[$SiC$_{16}$H$_{10}]$$^+$ (2) & 1.58 & 0.55 & 11.85 & +0.37 & 6.18 & --0.29\\ 
C$_{24}$H$_{12}$$^+$ & 5.24 & & 11.41 & & 6.38 & \\
$[$SiC$_{24}$H$_{12}]$$^+$ & 2.87 & 0.55 & 11.48 & +0.07 & 6.21 & --0.17\\
 & & & 11.32 & --0.09; new & & \\
C$_{32}$H$_{14}$$^+$ & 7.27 & & 11.11 & & 6.23 & \\
$[$SiC$_{32}$H$_{14}]$$^+$ (1) & 5.01 & 0.69 & 11.03 & --0.08 & 6.13 & --0.10\\
$[$SiC$_{32}$H$_{14}]$$^+$ (2) & 6.63 & 0.91 & 11.49 & +0.38 & 6.11 & --0.12\\
 & & & 10.79 & --0.33; new & & \\
$[$SiC$_{32}$H$_{14}]$$^+$ (3) & 5.34 & 0.73 & 11.15 & +0.04 & 6.13 & --0.10\\
 & & & 10.95 & --0.16; new & & \\
\hline
\end{tabular}}
\medskip
$^*$ All values are expressed in~$\mu$m.
\end{table}