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Abstract

Two topics of fundamental physics are considered where nuclides with a low ß-decay
energy are of high interest, namely nuclear astrophysics and neutrino physics. A few relevant
ground-to-ground ß-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 ¹²³Te, 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 ¹²³Te 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 _-transitions can be used for determination of the neutrino
rest mass. The decay energies (Q-values) of ¹³¹Cs and ²⁰²Pb were determined. It turned
out that the nuclide ²⁰²Pb can hardly be used for the neutrino mass determination due
to its too high Q-value, whereas ¹³¹Cs can be confidently excluded from the consideration
since the examined ß-transition is energetically forbidden. The directly measured Q-value of
187Re 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
ß^-spectra acquisition of ¹⁸⁷Re. 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.