element
Information about Terbium-138:

WikipediaNeutron Cross SectionsX-Ray TransitionsX-Ray Attenuation

    Mass-Energy Data:

    Atomic Mass:137.952870±0.000860amu #
    Excess Mass (Δ):-43.901000±0.801000MeV #
    Binding Energy:1106.891000±0.801000MeV #
"The 1995 update to the atomic mass evaluation" by G.Audi and A.H.Wapstra, Nuclear Physics A595 vol. 4 p.409-480, December 25, 1995.