\begin{table}%t1
\par
\caption{Equilibrium geometry (in $\AA$) dipole moment ($\mu$, in Debyes),
rotational constants ($B_{\rm e}$, $D_{\rm e}$ and $B_{0}$, in MHz), harmonic 
wavenumbers ($\omega_{i}$, in cm\textsuperscript{--1}), and intensities 
($I$, in Debyes$^2$/$\AA^{2}$ amu) of \textit{l}-SiCCC.
\label{tab1}}
%\centerline
 \begin{tabular}{c c c c c c c c c c c c c}    
\hline\hline
& & RCCSD(T) & RCCSD(T) & UCCSD(T) &CASSCF & CASSCF & CASSCF & MCSCF & CCSD(T) & MP2 & CISD & $m\omega^g$ \\
& & $cc-pVDZ^a$ & $cc-pVTZ^b$ & $cc-pVTZ^b$ & $cc-pVDZ^a$ & $cc-pVTZ^b$ & $cc-pVQZ^b$ &
6-31G$(d)^c$ & cc-pVQ$Z^d$ & 6-31G($d)^{e}$ & DZ$P^f$ & 
\\
\hline
$R_1$ & (Si-CCC str) &
    1.7662 &
    1.7447 &
    1.7427 &
    1.7531 &
    1.7410 &
    1.7197 &
    1.74   &
    1.7249 &
    1.732  &
    1.722  &
\\
$R_2$ & (SiC-CC str) &
    1.3299 &
    1.2959 &
    1.2954 &
    1.2966 &
    1.2841 &
    1.2956 &
    1.29   &
    1.2899 &
    1.297  &
    1.298
\\
$R_3$ & (SiCC-C str) &
    1.3120 &
    1.3108 &
    1.3133 &
    1.3111 &
    1.3003 &
    1.2987 &
    1.31   &
    1.3062 &
    1.3111 &
    1.3070 &
\\
$\mu$ & & & & & & 
    4.0293 &
    4.4064 &
& & & &
\\
$B_{\rm e}$& &
    2636.4 &
    2705.49 &
    2706.86 &
    2691.68 &
    2736.88 &
    2753.16 & & & & &
    2747.7085
\\
$B_0$& &
    2637.8  & & &
    2690.45  & & & & & &  &
\\
$D_{\rm e} \times 10^{-6}$& & 
    221.529 & & &
    218.844 & & & & & & &
    255.23  
\\
$\omega_1 (\sigma)$ & (C-C-C stretching) &
    2016.2 &
    2040  &
    1971  &
    2070.0 &
    2060 &
    2005 
    ($I=152$) &
    2055  & &
    2003 & &
\\
$\omega_2 (\sigma)$ & (Si-C stretching) &
    1368.8  &
    1391   &
    1318   &
    1357.1 &
    1365  &
    1366  ($I=11$) &
    1342  & &
    1332  & &
\\
$\omega_3 (\sigma)$ & (C-C-C stretching) &
    593.8 &
    612  &
    606  &
    611.3 &
    621 &
    639 
    ($I=4$) &
    613 & &
    629 & &
\\
$\omega_4 (\pi)$ & (trans-bending) &
    379.8  &
    384   &
    381   &
    443.1 &
    455 &
    463  
    ($I=9$) &
    382  & &
    380  & &
\\
$\omega_5 (\pi)$ & (cis-bending) &
    147.2  &
    147    &
    147    &
    166.9  &
    175   &
    166
    ($I=3$)  &
    150    &  &
    151  & &
\\
\hline
\end{tabular}
\par
\smallskip
$^a$ This work. Values derived from our 6D PES; $^b$ this work. Values obtained using standard approaches implemented in MOLPRO. Refs.
\citep{51} \citep{52}; $^c$ Ref. \citep{10}; 
$^d$ Ref. \citep{24};
$^e$ Ref. \citep{9};
$^f$ Ref. \citep{8};
$^g$ Ref. \citep{21}.
\end{table}