THE RADIOACTIVE ISOTOPES Al24, P28, Cl32

Abstract

The positron emitters P28 (0.29 ± 01 sec.) and Cl32 (0.32 ± 01 sec.) have been discovered in (p, n) reactions with thresholds at 15.4 ± 0.6 Mev. and 14.5 ± 0.6 Mev. respectively. Identification is realized through threshold and transition energies as well as through the complex γ-ray spectra identified in part with the known levels of the daughters Si28 and S32.The new nuclei represent an extension to the series A = 4k, Z = 2k + 1, whose initial members, B8, N12, Na20, are delayed α-emitters, while the recently reported Al24 is known to emit delayed alphas or protons.Under re-examination of Al24, a half-life of 2.0 ± 1 sec. is obtained for γ-ray activity which identifies the stable daughter Mg24.The results are in substantial agreement with the recent work of Glass, Jensen, and Richardson. Delayed α-particles are not observed with the new isotopes.