4.01 BE II
9 mass
1.5 spin
-0.0 log isotopic abundance         
       0.000  0.5 1s2.2s 2S   -625.01             VAPW                                  
   31928.744  0.5 1s2.2p 2P   -118.00             NTZA
   31935.320  1.5 1s2.2p 2P   -1.018      -2.299  Y                              

VAPW      Vetter, J., Ackermann, H., zu Putlitz, and Weber, E.W. 1976.  
          Z. Physik A 276, 161-165.      

Y         Yerokhin, V.A. 2008. Phys. Rev. A 78, 012513.

NTZA      Nortershauser, D., Tiedemann, D., Zakova, M,, Andjelkovic, A. et al. 2009.  
          Phys. Rev. Lett. 102, 062503.

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