The158Tb decay and the possibility of determining neutrino mass

High-precision direct gamma -ray and K X- gamma coincidence measurements have been performed in the electron-capture decay of 158Tb. A revised level scheme of 158Gd is proposed, with high-precision energies and intensities. The Q value determined for this decay using K capture to the high-lying levels in 158Gd shows that a K capture to the 1187 keV level is excluded. In addition the authors' K X- gamma coincidence measurements do not show any such event with an upper limit of 2*10-5 (90% CL).