The Radiations Emitted from Artificially Produced Radioactive Substances III. Details of the Beta-Ray Spectrum ofP32

Abstract

The high energy portion of the distribution of $\beta$-rays from ${\mathrm{P}}^{32}$ was investigated by means of a hydrogen-filled cloud chamber in a magnetic field. A Konopinski-Uhlenbeck distribution was followed practically to the cutoff of 8200 $H_{\rho }$ predicted by an extrapolation of the K-U plot. But it is possible to account for all tracks in excess of a straight line dropping to 6950 $H_{\rho }$ by a spreading due to the estimated probable error of ±3.8 percent. Accordingly, this work is best interpreted as indicating a sharp deviation from the K-U relation near the high energy limit, dropping to an upper limit of about 6950 $H_{\rho }$. This discrepancy might be eliminated by modifying the K-U formula to apply to a doubly forbidden type of disintegration. However, for the allowed transitions from ${\mathrm{N}}^{13}$ and ${\mathrm{F}}^{17}$, there is evidence from disintegration data that experimental upper limits are to be taken instead of the K-U extrapolations. The low energy part of the ${\mathrm{P}}^{32}$ $\beta$-spectrum was obtained from a very thin source suspended at the center of the expansion chamber. This distribution approached the origin almost as predicted by the K-U relation. There appeared to be no irregularities such as those observed by H. O. W. Richardson in the case of RaE.