Experimental Evidence for Orbital Electron Emission Accompanying Beta-Decay

Experiments are described which indicate the existence of a mode of beta-disintegration in which the energy emitted is shared by three particles: beta-particle, neutrino, and ejected orbital electron. The energy spectrum of the orbital electrons ("IB electrons") from Sc⁴⁴ has been measured over the range 30 to 150 kev. The "IB internal conversion coefficient"---that is, the ratio of the measured number of IB electrons to the number of internal bremsstrahlung (IB) predicted by the theory of Knipp and Uhlenbeck, and Bloch---is found to be essentially constant over the measured energy range, and equal to 4.3. The frequency with which the three-particle disintegration takes place is about 0.04 times that of ordinary decay into a beta-particle and a neutrino. The measurements have an estimated accuracy of +3 percent, -20 percent.