The ($p,n$) thresholds for the formation of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{P}$, ${}_{}{}^{32}{}_{}{}^{}\mathrm{Cl}$, and ${}_{}{}^{36}{}_{}{}^{}\mathrm{K}$ from targets of ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, and ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$, respectively, have been measured relative to the ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}\mathrm{}(p,n)\mathrm{}{}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ threshold by detecting $\beta$ rays from these short-lived activities. Half-lives were determined by multiscaling techniques. The resulting ($p,n$) thresholds (in keV), half-lives (in msec) are as follows: ${}_{}{}^{20}{}_{}{}^{}\mathrm{Na}$ (15419±6, 442±5); ${}_{}{}^{28}{}_{}{}^{}\mathrm{P}$ (15 666±6, 266±4); ${}_{}{}^{32}{}_{}{}^{}\mathrm{Cl}$ (13 902±9 and 13 978±16, 281±8); ${}_{}{}^{36}{}_{}{}^{}\mathrm{K}$ (13 976±8, 336±4). The half-life of ${}_{}{}^{24}{}_{}{}^{}\mathrm{Al}$ was measured as 2.054±0.009 sec.

• Received 17 June 1971

DOI:https://doi.org/10.1103/PhysRevC.4.1800