Search for Superscreening effect in Superconductor

Abstract

The decay of ${}^{19}$O($β^-$) and ${}^{19}$Ne($β^+$) implanted in niobium in its superconducting and metallic phase 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 one-sigma error bar. This measurement casts strong doubts on the predicted strong electron screening in superconductor, the so-called superscreening. The measured difference in screening potential energy is 110(90) eV for ${}^{19}$Ne and 400(320) eV for ${}^{19}$O. Precise determinations of the half-lives were obtained for ${}^{19}$O: 26.476(9) s and ${}^{19}$Ne: 17.254(5) s.

4 pages, 3 figures, accepted for publication in Physical Review Letters