\begin{table}%t1
\caption{\label{principal_lines}Principal lines in the 10.9--11.3~\AA\ region.} 
\par
%\centerline
{\small
\begin{tabular}{l l l l l}
\hline\hline\noalign{\smallskip}
Wavelength (\AA)\tablefootmark{a} & Ion &  Line label & Transition  \\
\hline\\[-3mm]
11.000 & Ne IX & $w4$ & $\rm 1s^2~  ^1S_0 {-} 1{\rm s} 4p~~ ^1P_1$  \\
11.003 & Na X & $w$ &   $\rm 1s^2~  ^1S_0 {-} 1{\rm s} 2p~~ ^1P_1$  \\
11.023 & Fe XVII & &    $\rm 2s^2~2p^6~^1S_0 {-} 2s~2p^6~4p~~^1P_1$ \\
11.080 & Na X & $x$ &   $\rm 1s^2~  ^1S_0 {-} 1{\rm s} 2p~~ ^3P_2$  \\
11.083 & Na X & $y$ &   $\rm 1s^2 ~ ^1S_0 {-} 1{\rm s} 2p~~ ^3P_1$  \\
11.133 & Fe XVII & &    $\rm 2s^2~2p^6~~^1S_0 {-} 2{\rm s}^2~2p^5~5d~~^1P_1$ \\
11.192 & Na X & $z$ &   $\rm 1s^2 ~ ^1S_0 {-} 1{\rm s} 2s~~ ^3S_1$  \\
11.253 & Fe XVII & &    $\rm 2s^2~2p^6~~^1S_0 {-} 2{\rm s}^2~2p^5~5d~~^3D_1$ \\
\hline
\end{tabular}}
\tablefoot{\tablefoottext{a}{Wavelengths from \cite{lan05}.}}
\end{table}