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Abstract

The ECHo Collaboration (Electron Capture ¹⁶³Ho aims to investigate the calorimetric spectrum following the electron capture decay of ¹⁶³Ho to determine the mass of the electron neutrino. The size of the neutrino mass is reflected in the endpoint region of the spectrum, i.e., the last few eV below the transition energy. To check for systematic uncertainties, an independent determination of this transition energy, the Q-value, is mandatory. Using the TRIGA-TRAP setup, we demonstrate the feasibility of performing this measurement by Penning-trap mass spectrometry. With the currently available, purified ¹⁶³Ho sample and an improved laser ablation mini-RFQ ion source, we were able to perform direct mass measurements of ¹⁶³Ho and ¹⁶³Dy with a sample size of less than 10¹⁷ atoms. The measurements were carried out by determining the ratio of the cyclotron frequencies of the two isotopes to those of carbon cluster ions using the time-of-flight ion cyclotron resonance method. The obtained mass excess values are ME(¹⁶³Ho)= −66379.3(9) keV and ME(¹⁶³Dy)= −66381.7(8) keV. In addition, the Q-value was measured for the first time by Penning-trap mass spectrometry to be Q = 2.5(7) keV