Masses and Decay of Al24, P28, Cl32, Sc40, and Their Tz=0 Analog States

Abstract

The $\beta$ spectra and $\gamma$ transitions in the decay of ${\mathrm{Al}}^{24}$, ${\mathrm{P}}^{28}$, ${\mathrm{Cl}}^{32}$, and ${\mathrm{Sc}}^{40}$, produced by the ($p,n$) reaction in the UCLA sector-focused cyclotron, have been measured with a wedge-gap magnetic spectrometer and a 3-${\mathrm{cm}}^3$ lithium-drifted germanium detector. An on-line SDS-925 computer was used to separate, by half-life analysis, the activity of interest from longer-lived contaminants. The half-lives were measured to an accuracy of 0.5% and decay schemes are proposed. The ground-state masses are determined to 25-40 keV. In all cases, observation of a superallowed $\beta$ transition unambiguously determines the $T=1\mathrm{}$, $T_z=O$ analog state. The excitation energies of these analog states are measured to an accuracy of 3 keV. Mass relationships are used to predict from these data the excitation energy of the first $T=2\mathrm{}$, $T_z=O$ analog states.