Characterization of the ^{163}Ho Electron Capture Spectrum: A Step Towards the Electron Neutrino Mass Determination

High-Precision Q-Value Measurement Confirms the Potential of ^{135}Cs for Absolute Antineutrino Mass Scale Determination

The ground-state-to-ground-state β-decay Q value of ^{135}Cs(7/2^{+})→^{135}Ba(3/2^{+}) has been directly measured for the first time. The measurement was done utilizing both the phase-imaging ion-cyclotron resonance technique and the time-of-flight ion-cyclotron resonance technique at the JYFLTRAP Penning-trap setup and yielded a mass difference of 268.66(30) keV between ^{135}Cs(7/2^{+}) and ^{135}Ba(3/2^{+}). With this very small uncertainty, this measurement is a factor of 3 more precise than the currently adopted Q value in the Atomic Mass Evaluation 2016. The measurement confirms that the first-forbidden unique β^{-}-decay transition ^{135}Cs(7/2^{+})→^{135}Ba(11/2^{-}) is a candidate for antineutrino mass measurements with an ultralow Q value of 0.44(31) keV. This Q value is almost an order of magnitude smaller than those of nuclides presently used in running or planned direct (anti)neutrino mass experiment.

Production and separation of 163Ho for nuclear physics experiments

This paper describes the production and chemical separation of the ¹⁶³Ho isotope that will be used in several nuclear physics experiments aiming at measuring the neutrino mass as well as the neutron cross section of the ¹⁶³Ho isotope. For this purpose, several batches of enriched ¹⁶²Er have been irradiated at the Institut Laue-Langevin high flux reactor to finally produce 6 mg or 100 MBq of the desired ¹⁶³Ho isotope. A portion of the Er/Ho mixture is then subjected to a sophisticated chemical separation involving ion exchange chromatography to isolate the Ho product from the Er target material. Before irradiation, a thorough analysis of the impurity content was performed and its implication on the produced nuclide inventory will be discussed.