\begin{table}%t6
%\centering
\par
\caption{Level populations 
of  the most spectroscopically-important levels 
(in decreasing order of level population),
calculated  at  10$^{10}$~\cmt\ and $T=1$~MK.
%
 The first two columns  list the 
 values $N_{j}$~[cm$^{-3}$] calculated  with the present ion model,  
 including all excitations between all the 54 levels 
(case A), and only excitations from the 
first three levels (case B, see also  Fig.~\ref{fig:balance}).
The last two columns report, for comparison, the values calculated 
by \cite{bhatia_doschek:95} [BD] and \cite{pelan_berrington:01} [PB] 
at a density of 10$^{10}$~\cmt. The metastable levels are marked~M.\label{tab:pop}} 
\begin{tabular}{@{}rccccl@{}}
\hline\hline\noalign{\smallskip}
   $i$   &  A     &  B   & BD & PB &  \\ 
%    & 10$^{8}$  & 10$^{10}$  & 10$^{10}$ & 10$^{10}$ & 10$^{10}$  \\
\hline\noalign{\smallskip}
1  & 0.67 &          0.46 &  0.72 & 0.62 &  \\ 
2 &  0.19 &          0.13 &  0.14 & 0.17  &  M \\ 
8 &  $3.9 \times 10^{-2}$ &  0.19 &   $4.2 \times 10^{-2}$ &  $8.7 \times  10^{-2}$  &  M \\ 
5 &  $3.1  \times 10^{-2}$ &  0.10 &  $2.9 \times 10^{-2}$ & $4.1 \times  10^{-2}$  &  M \\ 
10 & $1.9  \times 10^{-2}$ &  $6.8 \times  10^{-2}$ & $1.9 \times  10^{-2}$ & $3.7 \times   10^{-2}$  &  M \\ 
18 &  $1.7  \times 10^{-2}$ & $2.1 \times  10^{-2}$ & $2.0 \times  10^{-2}$ & $1.6 \times   10^{-2}$  &  M \\ 
20 &  $1.4  \times 10^{-2}$ & $1.4 \times  10^{-2}$ & $1.3 \times  10^{-2}$ & $1.3 \times   10^{-2}$  &  M \\ 
21 &  $1.2  \times 10^{-2}$ & $1.3 \times  10^{-2}$ & $1.3  \times 10^{-2}$ & $1.1 \times   10^{-2}$ &   M \\ 
24 &  $5.2  \times 10^{-3}$ & $3.8  \times 10^{-3}$ & $4.8  \times 10^{-3}$ & $3.9 \times   10^{-3}$ &   M \\ 
4 &   $5.7  \times 10^{-7}$ & $2.6  \times 10^{-7}$ & $1.5  \times 10^{-7}$ & $3.7 \times 10^{-7}$   & \\ 
6 &   $1.4 \times  10^{-7}$ &  $7.0 \times  10^{-8}$ & $ 1.  \times 10^{-7}$ & $1.2  \times 10^{-7}$  & \\ 
22 &  $8.3  \times 10^{-8}$ & $4.3 \times  10^{-8}$ &  $5.7  \times 10^{-8}$ & $4.5\times  10^{-7}$  & \\ 
%////
19 &  $3.4  \times 10^{-8}$ & $1.6  \times 10^{-8}$ &  $5.4 \times 10^{-9}$  & $1.3 \times   10^{-8}$  & \\ 
17 &  $1.4  \times 10^{-8}$ & $6.1  \times 10^{-9}$ & $1.2\times 10^{-8}$ &  $1.3  \times 10^{-8}$  & \\ 
%
15 &  $3.5  \times 10^{-9}$ & $1.9  \times 10^{-9}$ &  $2.3 \times10^{-9}$ & $2.2 \times  10^{-9}$  & \\ 
13 &  $2.9  \times 10^{-9}$ & $1.7 \times  10^{-9}$ & $1.7 \times 10^{-9}$ & $6.3  \times 10^{-9}$  & \\ 
\par
3 &  $1.5  \times 10^{-9}$ & $1.0  \times 10^{-9}$ &  $1.9 \times 10^{-9}$ & $1.4  \times 10^{-9}$  & \\ 
%
43 &  $7.3  \times 10^{-10}$ & $4.7  \times10^{-10}$ &  &     & \\ 
44 &  $3.6  \times 10^{-10}$ & $2.4 \times 10^{-10}$ &  &     & \\ 
%
30 & $2.5 \times  10^{-10}$ &  $1.7 \times10^{-10}$ &  $2.2\times 10^{-10}$ & $2.1 \times  10^{-10}$   & \\ 
28 &  $1.7  \times 10^{-10}$ & $1.2 \times10^{-10}$ & $1.7 \times 10^{-10}$ & $3.2  \times 10^{-12}$?  & \\ 
45 &  $1.3 \times  10^{-10}$ & $8.6 \times10^{-11}$ &    &   & \\ 
31 &  $9.9 \times  10^{-11}$ & $6.7 \times10^{-11}$ &  $6.3\times  10^{-11}$ & $7.5  \times  10^{-11}$  & \\ 
\par
27 &  $9.5  \times 10^{-11}$ & $6.5 \times10^{-11}$ & $ 8.4 \times 10^{-11}$ & $7.8 \times 10^{-11}$  & \\ 
29 &  $6.0  \times 10^{-11}$ & $4.1 \times10^{-11}$ & $3.9   \times 10^{-11}$ & $4.9  \times 10^{-11}$  & \\ 
\par
\noalign{\smallskip}
\hline
\end{tabular}
\end{table}