\begin{table}%t8 
\caption{\label{tab8}Comparison of effective collision strengths ($\Upsilon$) for some transitions  of Ar~XVII. ($a{\pm}b \equiv$ $a\times$10$^{{\pm}b}$).}
%\centering
\par
\begin{tabular}{rrllllll}                                                                        
\hline                                                                                              
\hline  
& &  \multicolumn{3}{c}{Present Results} &  \multicolumn{3}{c}{Keenan et~al. (1987)} \\  
\hline                                                                                           
\multicolumn{2}{c}{Transition} & \multicolumn{6}{c}{Temperature (log, K)}\\                                 
\hline                                                                                              
  $i$ & $j$ &  6.80	& 7.00 &     7.20   &  6.80	& 7.00 &     7.20 \\   
\hline                                                                                           
  1  &  2    &  1.118-3   &  9.531-4   &  7.946-4  &  9.454-4  &   8.319-4  &   7.184-4   \\
  1  &  3    &  4.873-4   &  4.345-4   &  3.729-4  &  4.385-4  &   3.931-4  &   3.444-4   \\
  1  &  4    &  1.568-3   &  1.408-3   &  1.224-3  &  1.356-3  &   1.246-3  &   1.131-3   \\
  1  &  5    &  1.847-3   &  1.876-3   &  1.886-3  &  1.641-3  &   1.673-3  &   1.724-3   \\
  1  &  6    &  2.417-3   &  2.157-3   &  1.847-3  &  2.191-3  &   1.963-3  &   1.719-3   \\
  1  &  7    &  6.271-3   &  6.979-3   &  7.698-3  &  6.053-3  &   6.694-3  &   7.655-3   \\
  1  &  8    &  2.717-4   &  2.352-4   &  1.995-4  &  1.428-4  &   1.385-4  &   1.307-4   \\
  1  &  9    &  1.306-4   &  1.174-4   &  1.016-4  &  7.931-5  &   7.679-5  &   7.179-5   \\
  1  & 10    &  4.002-4   &  3.625-4   &  3.173-4  &  2.527-4  &   2.484-4  &   2.379-4   \\
  1  & 11    &  3.803-4   &  3.854-4   &  3.841-4  &  2.193-4  &   2.462-4  &   2.732-4   \\
  1  & 12    &  6.360-4   &  5.715-4   &  4.945-4  &  2.917-4  &   3.081-4  &   3.068-4   \\
  1  & 13    &  6.430-5   &  5.353-5   &  4.327-5  & 	       &   	    &    	  \\
  1  & 14    &  1.086-4   &  9.390-5   &  8.029-5  & 	       &   	    &    	  \\
  1  & 15    &  1.435-4   &  1.198-4   &  9.700-5  & 	       &   	    &    	  \\
  1  & 16    &  1.173-4   &  1.119-4   &  1.086-4  & 	       &   	    &    	  \\
  1  & 17    &  1.270-3   &  1.404-3   &  1.518-3  &  9.962-4  &   1.143-3  &   1.345-3   \\
\hline                                                     				\end{tabular} 
\par
\end{table}