The NuclideP33and theP32Spectrum

${\mathrm{P}}^{33}$ has been produced by the bombardment of sulfur, sodium sulfide, and lithium chloride with the 48-Mev gamma-ray spectrum of the University of Chicago betatron. The reactions involved are ${\mathrm{S}}^{34}(\gamma ,p){\mathrm{P}}^{33}$, ${\mathrm{Cl}}^{35}(\gamma ,2p){\mathrm{P}}^{33}$, and ${\mathrm{Cl}}^{37}(\gamma ,\alpha ){\mathrm{P}}^{33}$. The ${\mathrm{P}}^{33}$ activity has a 25±2 day half-life with a 0.27±0.02-Mev negative beta-ray. There is less than one (0.5-Mev) gamma for every fifteen betas. The activity was observed in the presence of ${\mathrm{P}}^{32}$, and its ratio to the ${\mathrm{P}}^{32}$ activity did not change with chemical purification. Beta-ray spectra of the weak component observed in Oak Ridge carrier-free ${\mathrm{P}}^{32}$ indicate that this weak activity is ${\mathrm{P}}^{33}$ produced by the reaction ${\mathrm{S}}^{33}\mathrm{}(n,p)\mathrm{}{\mathrm{P}}^{33}$. The cross section for pile neutrons for this reaction is approximately 0.029 barn. The Fermi plot of the beta-ray spectrum is straight with a $log\mathrm{ft}$ value of 5.2. A decay scheme for ${\mathrm{P}}^{33}$ is proposed.