\begin{table}%t3
\par
\caption{Perturbatively computed fundamentals of \textit{l}-SiCCC. All values are in cm$^{-1}$.
\label{tab3}}
%\centerline
 {\begin{tabular}{c c c }
\hline \hline
&CASSCF/cc-pVD$Z^a$ & CASSCF/cc-pVT$Z^b$ 
\\
\hline
$\nu_1 (\sigma)$&
2034 &
2024 
\\
$\nu_2 (\sigma)$&
1344 &
1352
\\
$\nu_3 (\sigma)$&
601 &
611
\\
$\nu_4 (\pi)$&
422 &
434
\\
$\nu_5 (\pi)$&
160 &
169
\\
\hline
\end{tabular}}
\par
\smallskip
$^a$ Derived from our 6D-PESs;
$^b$ Estimations. See text for more details.
\end{table}