Electron capture beta decay of partially polarized nuclei

In this paper, we compute the spin excess for the neutrinos radiated in the process of electron capture beta decay of partially polarized nuclei. The results of computation are presented for the [Formula: see text] nuclei polarized by the strong hyperfine field in a ferromagnetic substance. This system was suggested as a possible source of monoenergetic neutrino radiation with a preferable direction of neutrino propagation. We directly compute the spin excess of radiated neutrinos and show that it is slightly greater than that estimated previously under simplifying assumptions.