The neutrino mass from the tritium beta spectrum in valine

Abstract The tritium beta spectrum in the valine molecule has been studied with the improved ITEP spectrometer. Emphasis has been put on the determination of the apparatus functions. An estimate resulting from the analysis is that the neutrino mass is larger than 20 eV. The mass difference of neutral 3 H and 3 He atoms calculated from the end-point energy is in good agreement with recent direct measurements of this value with an ion-cyclotron resonance spectrometer.