\begin{table}%t2
%\centering
\par
\caption{\label{tab_energy_si}The level energies (Ryd) of Si$^{4+}$ from different calculations along with the compilation of NIST v3$^2$.}
\begin{tabular}{ccccccc}
\hline\hline\noalign{\smallskip}
ID  &   Level~specification  & NIST\tablefootmark{a}  & AS  & FAC  & CHIANTI\tablefootmark{b}  &  MCHF\tablefootmark{c} \\
\hline\noalign{\smallskip}
   1 & ${\rm    2s^2 2p^6 ~ ^1S_0}$ &               &   0.000000   &  0.000000   &  0.000000   &           \\
   2 & ${\rm 2s^2 2p^5 3s ~ ^3P_2}$ &   7.636576    &   7.627520   &  7.645096   &  7.471944   &  7.636311 \\
   3 & ${\rm 2s^2 2p^5 3s ~ ^3P_1}$ &   7.660020    &   7.651149   &  7.669024   &  7.496347   &  7.659752 \\
   4 & ${\rm 2s^2 2p^5 3s ~ ^3P_0}$ &   7.682625    &   7.672594   &  7.689856   &  7.518236   &  7.682296 \\
   5 & ${\rm 2s^2 2p^5 3s ~ ^1P_1}$ &   7.732203    &   7.727683   &  7.750462   &  7.576521   &  7.731955 \\
   6 & ${\rm 2s^2 2p^5 3p ~ ^3S_1}$ &   8.258379    &   8.246423   &  8.256845   &  8.101019   &  8.258102 \\
   7 & ${\rm 2s^2 2p^5 3p ~ ^3D_3}$ &   8.364780    &   8.359913   &  8.372963   &  8.189849   &  8.364501 \\
   8 & ${\rm 2s^2 2p^5 3p ~ ^3D_2}$ &   8.374174    &   8.369346   &  8.384104   &  8.198962   &  8.373860 \\
   9 & ${\rm 2s^2 2p^5 3p ~ ^3D_1}$ &   8.391529    &   8.386711   &  8.399595   &  8.215911   &  8.391069 \\
  10 & ${\rm 2s^2 2p^5 3p ~ ^1D_2}$ &   8.422766    &   8.418290   &  8.434033   &  8.250539   &  8.422583 \\
  11 & ${\rm 2s^2 2p^5 3p ~ ^1P_1}$ &   8.437853    &   8.436352   &  8.450207   &  8.264883   &  8.437552 \\
  12 & ${\rm 2s^2 2p^5 3p ~ ^3P_2}$ &   8.451074    &   8.446452   &  8.462297   &  8.278670   &  8.450769 \\
  13 & ${\rm 2s^2 2p^5 3p ~ ^3P_0}$ &   8.454788    &   8.451684   &  8.464687   &  8.280566   &  8.454470 \\
  14 & ${\rm 2s^2 2p^5 3p ~ ^3P_1}$ &   8.460253    &   8.457485   &  8.472367   &  8.286872   &  8.459926 \\
  15 & ${\rm 2s^2 2p^5 3p ~ ^1S_0}$ &   8.77505     &   8.876968   &  8.922108   &  8.851711   &  8.774769 \\
  16 & ${\rm 2s^2 2p^5 3d ~ ^3P_0}$ &   9.273318    &   9.270566   &  9.267329   &  9.103458   &  9.273033 \\
  17 & ${\rm 2s^2 2p^5 3d ~ ^3P_1}$ &   9.278845    &   9.276363   &  9.272374   &  9.109172   &  9.278537 \\
  18 & ${\rm 2s^2 2p^5 3d ~ ^3P_2}$ &   9.290708    &   9.288542   &  9.284232   &  9.121027   &  9.290319 \\
  19 & ${\rm 2s^2 2p^5 3d ~ ^3F_4}$ &   9.307536    &   9.309413   &  9.305353   &  9.132764   &  9.307223 \\
  20 & ${\rm 2s^2 2p^5 3d ~ ^3F_3}$ &   9.316348    &   9.318389   &  9.316576   &  9.142041   &  9.316025 \\
  21 & ${\rm 2s^2 2p^5 3d ~ ^3F_2}$ &   9.333562    &   9.335089   &  9.332421   &  9.158398   &  9.333074 \\
  22 & ${\rm 2s^2 2p^5 3d ~ ^1F_3}$ &   9.345281    &   9.349206   &  9.347836   &  9.172796   &  9.345075 \\
  23 & ${\rm 2s^2 2p^5 3d ~ ^1D_2}$ &   9.380647    &   9.383311   &  9.381456   &  9.205793   &  9.379566 \\
  24 & ${\rm 2s^2 2p^5 3d ~ ^3D_1}$ &   9.380036    &   9.384037   &  9.383614   &  9.206276   &  9.380304 \\
  25 & ${\rm 2s^2 2p^5 3d ~ ^3D_3}$ &   9.384912    &   9.387550   &  9.386841   &  9.210350   &  9.384568 \\
  26 & ${\rm 2s^2 2p^5 3d ~ ^3D_2}$ &   9.389823    &   9.392712   &  9.392014   &  9.215362   &  9.389434 \\
  27 & ${\rm 2s^2 2p^5 3d ~ ^1P_1}$ &   9.449065    &   9.463153   &  9.471244   &  9.302779   &  9.448883 \\
  28 & ${\rm 2s^2 2p^5 4s ~ ^3P_2}$ &  10.01823     &  10.025722   & 10.021532   &             & 10.017768 \\
  29 & ${\rm 2s^2 2p^5 4s ~ ^3P_1}$ &  10.03067     &  10.038223   & 10.036309   &             & 10.030362 \\
  30 & ${\rm 2s^2 2p^5 4s ~ ^3P_0}$ &  10.06444     &  10.070616   & 10.066578   &             & 10.063904 \\
  31 & ${\rm 2s^2 2p^5 4s ~ ^1P_1}$ &  10.07483     &  10.081318   & 10.081030   &             & 10.074475 \\
  32 & ${\rm 2s^2 2p^5 4p ~ ^3S_1}$ &  10.24486     &  10.248513   & 10.246311   &             &           \\
  33 & ${\rm 2s^2 2p^5 4p ~ ^3D_3}$ &  10.27825     &  10.282198   & 10.285662   &             &           \\
  34 & ${\rm 2s^2 2p^5 4p ~ ^3D_2}$ &  10.28347     &  10.287772   & 10.292513   &             &           \\
  35 & ${\rm 2s^2 2p^5 4p ~ ^1P_1}$ &  10.29257     &  10.297196   & 10.302666   &             &           \\
  36 & ${\rm 2s^2 2p^5 4p ~ ^3P_2}$ &  10.29820     &  10.302854   & 10.309430   &             &           \\
  37 & ${\rm 2s^2 2p^5 4p ~ ^3P_0}$ &  10.32510     &  10.330410   & 10.337097   &             &           \\
  38 & ${\rm 2s^2 2p^5 4p ~ ^3D_1}$ &  10.32766     &  10.331017   & 10.335484   &             &           \\
  39 & ${\rm 2s^2 2p^5 4p ~ ^1D_2}$ &  10.33545     &  10.338814   & 10.345399   &             &           \\
  40 & ${\rm 2s^2 2p^5 4p ~ ^3P_1}$ &  10.33545     &  10.339068   & 10.344921   &             &           \\
  41 & ${\rm 2s^2 2p^5 4p ~ ^1S_0}$ &  10.43362     &  10.491684   & 10.528749   &             &           \\
  42 & ${\rm 2s^2 2p^5 4d ~ ^3P_0}$ &  10.59995     &  10.606728   & 10.600389   &             &           \\
  43 & ${\rm 2s^2 2p^5 4d ~ ^3P_1}$ &  10.60383     &  10.610847   & 10.604652   &             &           \\
  44 & ${\rm 2s^2 2p^5 4d ~ ^3P_2}$ &  10.61133     &  10.618787   & 10.613007   &             &           \\
  45 & ${\rm 2s^2 2p^5 4d ~ ^3F_4}$ &  10.61303     &  10.621538   & 10.616589   &             &           \\
  46 & ${\rm 2s^2 2p^5 4d ~ ^3F_3}$ &  10.61793     &  10.626940   & 10.623125   &             &           \\
  47 & ${\rm 2s^2 2p^5 4d ~ ^1D_2}$ &  10.62689     &  10.636085   & 10.632943   &             &           \\
  48 & ${\rm 2s^2 2p^5 4d ~ ^3D_3}$ &  10.63038     &  10.640347   & 10.638092   &             &           \\
  49 & ${\rm 2s^2 2p^5 4d ~ ^3D_1}$ &  10.64926     &  10.661087   & 10.660041   &             &           \\
  50 & ${\rm 2s^2 2p^5 4d ~ ^3F_2}$ &  10.66570     &  10.673565   & 10.670477   &             &           \\
  51 & ${\rm 2s^2 2p^5 4d ~ ^3D_2}$ &  10.66860     &  10.676813   & 10.674084   &             &           \\
  52 & ${\rm 2s^2 2p^5 4d ~ ^1F_3}$ &  10.66937     &  10.677815   & 10.675137   &             &           \\
  53 & ${\rm 2s^2 2p^5 4f ~ ^3D_1}$ &  10.68445     &  10.689679   & 10.689431   &             &           \\
  54 & ${\rm 2s^2 2p^5 4f ~ ^3D_2}$ &  10.68502     &  10.690324   & 10.690251   &             &           \\
  55 & ${\rm 2s^2 2p^5 4f ~ ^3G_5}$ &  10.68812     &  10.694274   & 10.694413   &             &           \\
  56 & ${\rm 2s^2 2p^5 4f ~ ^1G_4}$ &  10.68821     &  10.694326   & 10.694619   &             &           \\
  57 & ${\rm 2s^2 2p^5 4f ~ ^3D_3}$ &  10.69027     &  10.695958   & 10.696143   &             &           \\
  58 & ${\rm 2s^2 2p^5 4f ~ ^1D_2}$ &  10.69082     &  10.696471   & 10.697012   &             &           \\
  59 & ${\rm 2s^2 2p^5 4f ~ ^1F_3}$ &  10.69390     &  10.700062   & 10.700759   &             &           \\
  60 & ${\rm 2s^2 2p^5 4f ~ ^3F_4}$ &  10.69399     &  10.700209   & 10.700871   &             &           \\
  \hline
\end{tabular}
\tablefoot{\tablefoottext{a}{Sources of NIST v3 are from the work of %Martin \& Zalubas (
\citet{MZ83} and references therein.} \tablefoottext{b}{Theoretical energies from Bhatia et~al. (1985).} \tablefoottext{c}{Data is calculated with multiconfiguration Hartree-Fock (MCHF) or multiconfiguration Dirac-Fock (MCDF) method, and available from
website: \protect\url{http://atoms.vuse.vanderbilt.edu/}}}
\end{table}