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

Ranitzsch, P. C.; Hassel, C.; Wegner, M.; Hengstler, D.; Kempf, S.; Fleischmann, A.; Enss, C.; Gastaldo, L.; Herlert, A.; Johnston, K.

##### Abstract:
The isotope $^{163}$Ho is in many ways the best candidate to perform experiments to investigate the value of the electron neutrino mass. It undergoes an electron capture process to $^{163}$Dy with an energy available to the decay, Q$_{EC}$, of about 2.8 keV. According to the present knowledge, this is the lowest Q$_{EC}$ value for such transitions. Here we discuss a newly obtained spectrum of $^{163}$Ho, taken by cryogenic metallic magnetic calorimeters with $^{163}$Ho implanted in the absorbers and operated in anticoincident mode for background reduction. For the first time, the atomic deexcitation of the $^{163}$Dy daughter atom following the capture of electrons from the 5s shell in $^{163}$Ho, the OI line, was observed with a calorimetric measurement. The peak energy is determined to be 48 eV. In addition, a precise determination of the energy available for the decay Q$_{EC}$=(2.858±0.010$_{stat}$±0.05$_{syst}$)  keV was obtained by analyzing the intensities of the lines in the spectrum. This value is in good agreement with the measurement of the mass difference between $^{163}$Ho and $^{163}$Dy obtained by Penning-trap mass spectrometry, demonstrating the reliability of the calorimetric technique.

 Zugehörige Institution(en) am KIT Institut für Mikro- und Nanoelektronische Systeme (IMS) Publikationstyp Zeitschriftenaufsatz Publikationsdatum 22.09.2017 Sprache Englisch Identifikator ISSN: 0031-9007, 1079-7114, 1092-0145 KITopen-ID: 1000125019 Erschienen in Physical review letters Verlag American Physical Society (APS) Band 119 Heft 12 Seiten Art.Nr.: 122501 Vorab online veröffentlicht am 19.09.2017 Externe Relationen Siehe auch Nachgewiesen in Web of ScienceDimensionsScopus
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