\begin{table}%t2
%\centering
\par
\caption{Ionic species of iron at 20~MK.\label{tab2}}
\begin{tabular}{ccccccc}
\hline\hline\noalign{\smallskip}
Element & $Z-z$ & $Z_{\rm eff}$ & $\Phi_{Z_{\rm eff}}$ & $A_z$ & $A_zZ_{\rm eff}^4$ & $V_z = Z_{\rm eff}^2\chi$ (keV)\\
\hline
\noalign{\smallskip}
Fe XXII & 21 & 21.98 & 0.05 & 0.43 $\times$ $10^{-5}$ & 1.004 & 6.57\\
Fe XXIII & 22 & 22.61 & 0.14 & 1.21 $\times$ $10^{-5}$ & 3.152 & 6.95\\
Fe XXIV & 23 & 23.20 & 0.25 & 2.15 $\times$ $10^{-5}$ & 6.232 & 7.32\\
Fe XXV & 24 & 23.77 & 0.56 & 4.82 $\times$ $10^{-5}$ & 15.381 & 7.68\\
\hline
\end{tabular}
\end{table}