\begin{table}%T6 \caption{\label{table6}Atomic data.} \small%\centering \par \begin{tabular}{lllll} \hline\hline & \multicolumn{2}{c}{CELs} & \multicolumn{2}{c}{ORLs} \\ Ion & Trans. Probabilities & Coll. strengths & Eff. recomb. coeffs. & Comments \\ \hline C$^{++}$& \nodata & \nodata & \citet{daveyetal00} & Case B \\ C$^{3+}$& \nodata & \nodata & \citet{pequignotetal91} & Case A \\ C$^{4+}$& \nodata & \nodata & \citet{pequignotetal91} & Case A \\ N$^{+}$ & \citet{wieseetal96} & \citet{lennonburke94} & \nodata & \\ N$^{++}$& \nodata & \nodata & \citet{kisieliusstorey02} & Case B; triplets\\ & & & \citet{escalantevictor90} & Case A; singlets\\ N$^{3+}$& \nodata & \nodata & \citet{pequignotetal91} & Case A \\ O$^{+}$ & \citet{zeippen82} & \citet{pradhanetal06} & \nodata & \\ O$^{++}$& \citet{wieseetal96} & \citet{aggarwalkeenan99}& \citet{storey94} & Case B; quartets\\ & \citet{storeyzeippen00}& & \citet{liuetal95} & Case A; doublets\\ O$^{3+}$& \nodata & \nodata & \citet{pequignotetal91} & Case A \\ Ne$^{++}$& \citet{balujazeippen88}& \citet{mclaughlinbell00}& Kisielius \& Storey (unpublished)& Case A; quartets\\ Ne$^{3+}$& \citet{zeippen82} & \citet{giles81} & \nodata & \\ Ne$^{4+}$&\citet{baluja85} & \citet{griffinbadnell00}& \nodata & \\ S$^{+}$ &\citet{mendozazeippen82a}& \citet{keenanetal96}& \nodata & \\ S$^{++}$&\citet{mendozazeippen82a}& \citet{tayalgupta99}& \nodata & \\ Cl$^{++}$&\citet{mendoza82} & \citet{mendoza83} & \nodata & \\ Cl$^{3+}$&\citet{mendozazeippen82a}& \citet{galavisetal95}& \nodata & \\ &\citet{kaufmansugar86}& & \nodata & \\ Ar$^{++}$&\citet{mendozazeippen83}& \citet{galavisetal95}& \nodata & \\ Ar$^{3+}$&\citet{mendozazeippen82a}& \citet{ramsbottometal97}& \nodata & \\ Ar$^{4+}$&\citet{mendozazeippen82a}&\citet{galavisetal95}& \nodata & \\ \hline \end{tabular} \end{table}