The Average Energy of Beta-Ray Spectra

The average beta-energy per disintegration has been measured for P³², Y⁹⁰, I¹³¹, and Ca⁴⁵. An air-filled water-electrode extrapolation ionization chamber was used for measurement of the rate of emission of energy. The absolute disintegration rate was determined by 4π-counting. Good agreement was found between the measured average energy values and values predicted by the Fermi theory using maximum energy data from the literature. Experimental results obtained were P³², 0.696±{}0.03 Mev; Y⁹⁰, 0.895±{}0.035 Mev; I¹³¹, 0.189±{}0.008 Mev (includes conversion electrons); and Ca⁴⁵, 0.0746±{}0.003 Mev.