Atomic corrections for the unique first-forbidden β transition of Re187

The shape of the spectrum of electrons emitted in β decay near the highest (endpoint) energy offers a direct way to determine the absolute values of neutrino masses. The authors reexamine one of the most promising candidates for determining the neutrino mass scale, the unique first-forbidden β transition from ¹⁸⁷Re(5/2⁺) to ¹⁸⁷Os(1/2^-). Their results show that exchange effects between the emitted electrons and the atomic bound electrons can considerably impact the shape of the electron spectrum near the endpoint. The authors conclude that atomic effects, especially the exchange effect, should be considered in current and future investigations of the neutrino mass scale from β decays.