\begin{table}%t1
 \caption{\label{tab:table1}Periods associated with the unstable
and stable eigenvalues (minutes) for $B_{00}=11$~G.}
 \small%\centering
\par
\begin{tabular}{cccccccccccc}
\hline\hline
 $P_{1}$&$P_{2}$&$P_{3}$&$P_{4}$&$P_{5}$&$P_{6}$&$P_{7}$&$P_{8}$&$P_{9}$&$P_{10}$&$P_{11}$&$P_{12}$
\\
 \hline $36. \ i $&$6.6 \ i$&$4.3 \ i$&$3.4 $&$3.1 $&$1.8$&$1.4 $&$1.3 $&$1.0 $&$0.0$&$0.0$&$0.0$ \\ \hline
\end{tabular}
\end{table}