Level energy(keV) Spin & Parity ---------------------------------------- ground state 0+Mass (The Ame2012 atomic mass evaluation (II) by M.Wang, G.Audi, A.H.Wapstra, F.G.Kondev, M.MacCormick, X.Xu, and B.Pfeiffer Chinese Physics C36 p. 1603-2014, December 2012)
254.100053 ± 0.000304 (amu) [mass excess = 93198 ± 283 (keV) ] [These values were derived from systematical trend]Evaluated Data Libraries
Links to the libraries.