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

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 beta-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 beta-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 194Hg and (194)Au. The new Q(EC)-value of 29(4) key 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. (C) 2010 Elsevier B.V. All rights reserved