Nature(London) 573, 243 (2019)

B.Seiferle, L.von der Wense, P.V.Bilous, I.Amersdorffer, C.Lemell, F.Libisch, S.Stellmer, T.Schumm, C.E.Dullmann, A.Palffy, P.G.Thirolf

Energy of the ²²⁹Th nuclear clock transition

RADIOACTIVITY ²²⁹Th(IT); measured decay products, Eγ, Iγ; deduced transition energy of this isomeric state to the ground state with an uncertainty of 0.17 electronvolts (one standard deviation) using spectroscopy of the internal conversion electrons emitted in flight during the decay of neutral ^229mTh atoms.

doi: 10.1038/s41586-019-1533-4