High energy resolution calorimetrically measured 193Pt electron capture spectrum

The radionuclide 163Ho, undergoing electron capture, has optimum properties to be used in experiments for the determination of the neutrino mass scale. This stems from its very low value Q-value, QEC ~ 2.83 keV which is very close to the binding energy of the 3s electrons. QEC is the maximum energy available for atomic excitations (assuming massless neutrinos), hence electrons from the K and L shells cannot be captured. Only one other nuclide, undergoing electron capture to the nuclear ground state of the daughter nucleus, has a QEC value which does not allow for K-captures, namely 193Pt. A high energy resolution calorimetric measurement of the 193Pt electron capture spectrum is of major importance to test the models for the description of low energy electron capture processes. We present a 193Pt spectrum obtained with low temperature metallic magnetic calorimeters with 193Pt ion-implanted in gold absorbers. We discuss the obtained results in comparison with the available high energy resolution 163Ho electron capture spectra.