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 ${\mathrm{Sc}}^{44}$ 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.