\begin{table}%t1
\par
\caption {\label{tab1}The SUMER spectral lines and the parameter values given by
PNN.}
\smallskip
  %\centerline
 { \begin{tabular}{c c c c} \hline\hline
SUMER spectra  & \multicolumn{3}{c}{PNN outputs$^1$}\\
lines & $\alpha$ & $\tau$ & $p_f$ \\
\hline  
\FeXIX & 2.5 {\bf 2.8} 3.1  & 9 {\bf 14} 20 & 0.1 {\bf 0.2} 0.7 \\
\CaXIII & 2.6 {\bf 2.8} 3.0 & 41 {\bf 45} 45 & 0.8 {\bf 0.9} 0.9 \\
%\SiIII
 Si\ts$\scriptstyle{\rm III}$
 & 2.4 {\bf 2.6} 2.8 & 5 {\bf 9} 12  & 0.2 {\bf 0.3} 0.9 \\
 \hline
\end{tabular}}
\par
\smallskip
$^1$ The most frequent values are given in bold, and the minimum and maximum
on
the left and right. $\tau$ is per exposure time (90~s) and $p_f$ is
per exposure time per
 5\arcsec~$\times$~4\arcsec\ spatial element.
\end{table}