Direct mass measurements of 194Hg and 194Au: A new route to the neutrino mass determination?

Abstract The study of nuclear electron capture (EC) offers an exciting alternative for the determination of the neutrino mass. Whereas only tritium and 187 Re can be used in the case of β -decay experiments involving the anti-neutrino, a potentially large number of EC-nuclides can be used in experiments involving the monochromatic neutrino. This alternative to β -decay experiments requires an accurate measurement of Q EC -values of appropriate candidates. In the present work we initiate a search for such a candidate and determined the Q EC -value of the electron capture in 194 Hg by direct mass measurements of 194 Hg and 194 Au. The new Q EC -value of 29(4) keV determined by the ISOLTRAP Penning-trap mass spectrometer at ISOLDE/CERN forbids the K-capture for 194 Hg. However, it allows a determination of the neutrino mass by a combination of a micro-calorimetric measurement of the de-excitation spectrum from L -capture in 194 Hg and a comparable Q EC -value remeasurement by high-precision Penning trap mass spectrometry.