Measurements of low decay energies of beta-processes using Penning traps

Two topics of fundamental physics are considered where nuclides with a low $\beta$-decay energy are of high interest, namely nuclear astrophysics and neutrino physics. A few relevant ground-to-ground $\beta$-transitions were addressed by Penning-trap mass spectrometry (PT-MS), employing the Shiptrap (GSI, Darmstadt) and Isoltrap (CERN, Geneva) facilities. In nuclear astrophysics the decay energy of a nuclide is an important spectroscopic parameter. Thus, in the case of the pure s-process nuclide ${}^{123}$Te, it was shown that when its decay energy is accurately and precisely known, the complete decay scheme in a hot stellar environment can be reliably reconstructed. It is shown that at typical s-process conditions the half-life of ${}^{123}$Te can be by many orders of magnitude shorter than the terrestrial value. This circumstance may be used, for example, for tests of astrophysical models in the A = 123 mass region. In neutrino physics, low-energy $\beta$-transitions can be used for determination of the neutrino rest mass. The decay energies (Q-values) of ${}^{131}$Cs and ${}^{202}$Pb were determined. It turned out that the nuclide ${}^{202}$Pb can hardly be used for the neutrino mass determination due to its too high Q-value, whereas ${}^{131}$Cs can be confidently excluded from the consideration since the examined $\beta$-transition is energetically forbidden. The directly measured Q-value of ${}^{187}$Re has shown that on the level of our present accuracy of 33 eV there are no unexpected systematic effects inherent in cryogenic microcalorimetry (CM), which was used for the ${\beta }^{-}$-spectra acquisition of ${}^{187}$Re. A specific problem in neutrino physics is the existence of sterile neutrinos, especially those which can contribute to the so-called Warm Dark Matter. It is shown that the combined efforts of PT-MS and CM may contribute to the keV sterile neutrino search in electron capture in a variety of nuclides.