Abstract
The decay of and implanted in niobium in its superconducting and metallic phases was measured using purified radioactive beams produced by the SPIRAL GANIL facility. Half-lives and branching ratios measured in the two phases are consistent within a error bar. This measurement casts strong doubts on the predicted strong electron screening in a superconductor, the so-called superscreening. The measured difference in screening potential energy is 110(90) eV for and 400(320) eV for . Precise determinations of the half-lives were obtained for , 26.476(9) s, and for , 17.254(5) s.
- Received 24 October 2012
DOI:https://doi.org/10.1103/PhysRevLett.110.032501
© 2013 American Physical Society