\begin{table}%t1
%\centering
\par
\caption{Some relevant energy levels and ionization potentials (in eV) from our MCDF calculations and from \citet{nist} for B-like ions. The energy of each term is obtained as the mean of the energy levels pondered by their statistical weight.\label{tab1}}
\begin{tabular}{lllllll}
\hline\hline
& \multicolumn{2}{c}{N$^{2+}$} & \multicolumn{2}{c}{O$^{3+}$} & \multicolumn{2}{c}{F$^{4+}$} \\
Level & MCDF & NIST & MCDF & NIST & MCDF & NIST \\
\hline
2s$^{2}$2p $^{2}$P & 0& 0& 0& 0& 0& 0 \\
2s2p$^{2}$ ${^4}$P & 6.70 & 7.10 &8.52 & 8.88 &10.34 &10.69\\
$E_{\rm IP}$ (2s$^2$ $^1$S) & 46.92 &47.45& 76.14& 77.41& 113.96& 114.24\\
$E_{\rm IP}$ (2s2p $^{3}$P) & 53.19& 55.80 &86.60 &87.61 & 123.22 & 126.25\\
$E_{\rm IP}$ (1s$^{2}$2s2p $^{1}$P) & 62.41 & 63.65 & 96.93 & 97.10 & 135.82 & 137.41\\
$\Delta E _{\rm IP} (^1{\rm P} -^3{\rm P})$ & 9.22 & 7.85 & 10.33 & 9.49 & 12.60 & 11.25 \\
	\hline
	\end{tabular}
\end{table}