THE MASS OF THE ELECTRON NEUTRINO FROM ELECTRON-CAPTURE IN HO-163

Using an M X-ray spectrum from electron capture in Ho-163 together wit h M X-ray fluorescence spectra of the Dy atom, the partial decay const ants of Ho-163, lambda(M1) and lambda(M2) were measured. With lambda(M 1), lambda(M2) and lambda(t) (total decay constant) as three constrain ts, the mass of the electron neutrino, m(V(e)) the Q-value, and log(ft ) of the Ho-163 decay were simultaneously determined. Results obtained are m(V(e)) = 110(-110)+350 eV, Q = 2.710(-0.005)+0.100) keV, and log (ft) = 4.993(-0.001)+0.030.