Das Positronenspektrum von22Na und die Ruhemasse des Neutrinos aus dem β+-Zerfall

Theβ+ spectrum of22Na has been measured with the Heidelberg (π/2) √13 iron-freeβ-ray spectrometer. Particular attention was paid to the upper end of the continuum. The maximum energy was found to beEmax=(545.7 ±0.5) keV. The rest mass of the neutrino connected withβ+ decay was found to be zero with an upper limit of 4.1 keV (67 per cent confidence).