\begin{table}%t6
\par
\caption {\label{table:j-index}Fine-structure energy levels for the current calculation compared to the earlier works of \cite{bhatia}, \cite{tachiev} [T\&F] and \cite{butler} [B\&Z], along with the observed values from NIST.}
%\centering
\par
\begin{tabular}{c@{\extracolsep{0.1cm}}l@{\extracolsep{0.1cm}}c@{\extracolsep{0.1cm}}c@{\extracolsep{0.2cm}}
c@{\extracolsep{0.2cm}}c@{\extracolsep{0.2cm}}c@{\extracolsep{0.2cm}}c@{\extracolsep{0.2cm}}c}
\hline\hline 
 & & & & \multicolumn{5}{c}{Energy levels (in Rydbergs)}\\
 & $LS$ state & $J$-value & $J$-index & This work & Bhatia & T\&F & NIST & B\&Z \\[5pt] 
\hline 
\par
 1 & 2s$^2$2p$^4~^3$P         & 2 &  1 & 0.00000 & 0.00000 & 0.00000 & 0.00000 & 0.00000 \\
   &                           & 1 &  2 & 0.01551 & 0.01733 & 0.01620 & 0.01625 & 0.01606 \\
   &                           & 0 &  3 & 0.02242 & 0.02451 & 0.02284 & 0.02298 & 0.02280 \\
 2 & 2s$^2$2p$^4~^1$D         & 2 &  4 & 0.34456 & 0.35729 & 0.32995 & 0.32738 & 0.32895 \\
 3 & 2s$^2$2p$^4~^1$S         & 0 &  5 & 0.71890 & 0.70981 & 0.70434 & 0.70422 & 0.72316 \\
 4 & 2s2p$^5~^3$P$^{\rm o}$   & 2 &  6 & 2.58447 & 2.67624 & 2.58701 & 2.58082 & 2.65633 \\
   &                           & 1 &  7 & 2.59933 & 2.69182 & 2.60169 & 2.59555 & 2.67143 \\
   &                           & 0 &  8 & 2.60693 & 2.70024 & 2.60970 & 2.60360 & 2.67914 \\
 5 & 2s2p$^5~^1$P$^{\rm o}$   & 1 &  9 & 3.66411 & 3.81440 & 3.63666 & 3.62212 & 3.73916 \\
 6 & 2p$^6~^1$S               & 0 & 10 & 6.06366 & 6.38065 & 6.06759 & 6.04143 & 6.39714 \\
 7 & 2s$^2$2p$^3$($^4$S$^{\rm o}$)3s~$^5$S$^{\rm o}$ & 1 & 11 & 6.07671 & 5.97177 & 6.09424 &         &  \\
 8 & 2s$^2$2p$^3$($^4$S$^{\rm o}$)3s~$^3$S$^{\rm o}$ & 1 & 12 & 6.22702 & 6.12989 & 6.23647 & 6.23800 &  \\
 9 & 2s$^2$2p$^3$($^2$D$^{\rm o}$)3s~$^3$S$^{\rm o}$ & 1 & 13 & 6.65627 & 6.53964 & 6.63381 & 6.63167 &  \\
   &                                                  & 2 & 14 & 6.65665 & 6.53999 & 6.63396 & 6.63186 &  \\
   &                                                  & 3 & 15 & 6.65751 & 6.54094 & 6.63416 & 6.63204 &  \\ 
10 & 2s$^2$2p$^3$($^4$S$^{\rm o}$)3p~$^5$P           & 1 & 16 & 6.66927 & 6.54769 & 6.66818 &         &  \\
   &                                                  & 2 & 17 & 6.67012 & 6.54880 & 6.66929 &         &  \\
   &                                                  & 3 & 18 & 6.67174 & 6.55052 & 6.67114 &         &  \\
11 & 2s$^2$2p$^3$($^2$D$^{\rm o}$)3s~$^1$D$^{\rm o}$ & 2 & 19 & 6.73158 & 6.61893 & 6.79805 & 6.70279 &  \\
12 & 2s$^2$2p$^3$($^4$S$^{\rm o}$)3p~$^3$P           & 1 & 20 & 6.80585 & 6.69894 & 6.79836 &         &  \\
   &                                                  & 0 & 21 & 6.80597 & 6.69925 & 6.79836 &         &  \\
   &                                                  & 2 & 22 & 6.80621 & 6.69952 & 6.79859 &         &  \\
13 & 2s$^2$2p$^3$($^2$P$^{\rm o}$)3s~$^3$P$^{\rm o}$ & 0 & 23 & 6.94104 & 6.76593 & 6.89537 & 6.89415 &  \\
   &                                                  & 1 & 24 & 6.94150 & 6.76641 & 6.89562 & 6.89434 &  \\
   &                                                  & 2 & 25 & 6.94255 & 6.76760 & 6.89641 & 6.89502 &  \\
14 & 2s$^2$2p$^3$($^2$P$^{\rm o}$)3s~$^1$P$^{\rm o}$ & 1 & 26 & 7.01977 & 6.84813 & 6.97024 & 6.96780 &  \\
15 & 2s$^2$2p$^3$($^2$D$^{\rm o}$)3p~$^1$P           & 1 & 27 & 7.18155 & 7.05039 & 7.14752 &         &  \\
16 & 2s$^2$2p$^3$($^2$D$^{\rm o}$)3p~$^3$D           & 1 & 28 & 7.20265 & 7.07066 & 7.16887 &         &  \\
   &                                                  & 2 & 29 & 7.20307 & 7.07070 & 7.16891 &         &  \\
   &                                                  & 3 & 30 & 7.20634 & 7.07445 & 7.17145 &         &  \\
17 & 2s$^2$2p$^3$($^2$D$^{\rm o}$)3p~$^3$F           & 2 & 31 & 7.24875 & 7.11453 & 7.21044 &         &  \\
   &                                                  & 3 & 32 & 7.25034 & 7.11618 & 7.21150 &         &  \\
   &                                                  & 4 & 33 & 7.25238 & 7.11827 & 7.21284 &         &  \\
18 & 2s$^2$2p$^3$($^2$D$^{\rm o}$)3p~$^1$F           & 3 & 34 & 7.27388 & 7.14257 & 7.23497 &         &  \\
19 & 2s$^2$2p$^3$($^2$D$^{\rm o}$)3p~$^3$P           & 0 & 35 & 7.40007 & 7.29152 & 7.35848 &         &  \\
   &                                                  & 2 & 36 & 7.40057 & 7.29650 & 7.35859 &         &  \\
   &                                                  & 1 & 37 & 7.40101 & 7.30375 & 7.35964 &         &  \\
\par
\hline
\end{tabular}
\end{table}