\begin{table}%t7
%%\centering
\caption{Ionic abundances from ORLs. \label{orl_ab}}
%\centerline
\begin{tabular}{llcl}
\hline\hline\noalign{\smallskip}
{Ion} & {$\lambda$} & {$I(\lambda)$}&
{$N$(X$^{i+}$)/$N$(H$^+$)} \\
 & {({\AA})} &
{[$I({\rm H}\beta)=100$]} & \\
\hline\noalign{\smallskip}
He$^{+}$  & 4471 & 3.222& $5.63\times10^{-2}$\\
          & 6678 & 2.538& $5.82\times10^{-2}$\\
          & 5876 & 10.87& $5.80\times10^{-2}$\\
          &adopted &      & $5.80\times10^{-2}$\\
He$^{2+}$ & 4686 & 47.75& $4.04\times10^{-2}$\\
          & 4860 & 2.833& $4.39\times10^{-2}$\\
&adopted         &      & $4.10\times10^{-2}$\\
C$^{2+}$  & 3918 & 0.024& $1.04\times10^{-3}$\\
          & 4267 & 0.575& $6.40\times10^{-4}$\\
          & 4802 & 0.032& $1.01\times10^{-3}$\\
          & 5342 & 0.034& $7.15\times10^{-4}$\\
          & 6462 & 0.060& $6.64\times10^{-4}$\\
          & 6578 & 0.231& $3.99\times10^{-4}$\\
          & 7231 & 0.108& $2.56\times10^{-4}$\\
&adopted         &      & $5.54\times10^{-4}$\\
C$^{3+}$  & 4070 & 0.425& $2.70\times10^{-4}$\\
          & 4187 & 0.197& $2.70\times10^{-4}$\\
          & 8196 & 0.289& $6.20\times10^{-4}$\\
&adopted         &      & $3.87\times10^{-4}$\\
C$^{4+}$  & 4658 & 0.579$^{a}$& $2.81\times10^{-4}$\\
N$^{2+}$  & 3995 & 0.009& $8.49\times10^{-5}$\\
          & 4041 & 0.012& $8.42\times10^{-5}$\\
          & 4043 & 0.008& $7.41\times10^{-5}$\\
          & 4678 & 0.007& $1.18\times10^{-4}$\\
          & 4179 & 0.005& $7.62\times10^{-5}$\\
          & 4237 & 0.005& $5.07\times10^{-5}$\\
          & 4431 & 0.006& $9.75\times10^{-5}$\\
          & 4631 & 0.021& $8.86\times10^{-5}$\\
          & 5667 & 0.014& $6.03\times10^{-5}$\\
          & 5680 & 0.033& $7.60\times10^{-5}$\\
          & 5686 & 0.019& $2.47\times10^{-4}$\\
          & 5927 & 0.002& $6.83\times10^{-5}$\\
          & 5940 & 0.004& $1.37\times10^{-4}$\\
          & 6482 & 0.004& $9.90\times10^{-5}$\\
&adopted         &      & $1.03\times10^{-4}$\\
N$^{3+}$  & 4379 & 0.059$^{b}$& $2.56\times10^{-5}$\\
N$^{4+}$  & 3483 & 0.031& $1.22\times10^{-5}$\\
\hline
          & 4707 & 0.015& $2.34\times10^{-5}$\\
          & 7582 & 0.011& $2.29\times10^{-5}$\\
          & 7703 & 0.021& $1.66\times10^{-5}$\\
&adopted         &      & $1.68\times10^{-5}$\\
N$^{5+}$  & 4945 & 0.043& $7.02\times10^{-6}$\\
O$^{2+}$  & 4072 & 0.134& $5.55\times10^{-4}$\\
          & 4111 & 0.012& $5.04\times10^{-4}$\\
          & 4119 & 0.035& $3.99\times10^{-4}$\\
          & 4133 & 0.013& $2.40\times10^{-4}$\\
          & 4153 & 0.021& $2.72\times10^{-4}$\\
          & 4317 & 0.022& $2.80\times10^{-4}$\\
          & 4320 & 0.026& $3.06\times10^{-4}$\\
          & 4346 & 0.017& $2.17\times10^{-4}$\\
          & 4349 & 0.041& $2.08\times10^{-4}$\\
          & 4367 & 0.035& $4.41\times10^{-4}$\\
          & 4639 & 0.070& $6.38\times10^{-4}$\\
          & 4649 & 0.165& $3.13\times10^{-4}$\\
          & 4662 & 0.036& $2.56\times10^{-4}$\\
          & 4676 & 0.037& $3.14\times10^{-4}$\\
&adopted         &      & $3.95\times10^{-4}$\\
O$^{3+}$  & 4435 & 0.019& $4.04\times10^{-5}$\\
          & 5592$^{c}$ & 0.105& $6.20\times10^{-5}$\\
&adopted         &      & $4.04\times10^{-5}$\\
O$^{4+}$  & 3410 & 0.103& $1.43\times10^{-5}$\\
          & 4632 & 0.188& $1.19\times10^{-5}$\\
&adopted         &      & $1.27\times10^{-5}$\\
O$^{5+}$  & 7611 & 0.014& $7.46\times10^{-6}$\\
Ne$^{2+}$ & 3327 & 0.016& $8.86\times10^{-5}$\\
          & 3335 & 0.042& $6.24\times10^{-5}$\\
          & 3355 & 0.027& $7.68\times10^{-5}$\\
          & 3694 & 0.023& $6.78\times10^{-5}$\\
          & 3777 & 0.011& $8.35\times10^{-5}$\\
          & 4392 & 0.011& $8.43\times10^{-5}$\\
          & 4409 & 0.017& $1.96\times10^{-4}$\\
&adopted         &      & $8.63\times10^{-5}$\\
Mg$^{2+}$ & 4481 & 0.023& $2.43\times10^{-5}$\\\hline
\end{tabular}
\medskip
$^{a}$ Corrected for a $23\%$ contribution from the [\ion{Fe}{iii}]
  $\lambda$4658 line, assuming [\ion{Fe}{iii}] $I(\lambda4658)/I(\lambda4734)=5.33$.\\
$^{b}$ Corrected for a total of $11\%$ contribution from the
\ion{C}{iii} and \ion{Ne}{ii} $\lambda$4380 lines, assuming
\ion{C}{iii} $I(\lambda4380)/(\lambda4383)=3.5$ and
\ion{Ne}{ii} $I(\lambda4380)/(\lambda4392)=0.61$.\\
$^{c}$ Also excited partly by charge exchange with H$^0$ \citep{liu1993}.
\end{table}