We have produced very large nuclear alignments in radioactive ${}_{}{}^{36}{}_{}{}^{}\mathrm{K}$ (half-life 0.34 sec) through laser optical pumping techniques. The ${}_{}{}^{36}{}_{}{}^{}\mathrm{K}$ was created through (p,n) reactions using a 50 nA, 22 MeV proton beam, and a 3.3 atmosphere ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$ target. Measurements were made with the target cell at room temperature, when direct optical pumping produces nuclear orientation in the ${}_{}{}^{36}{}_{}{}^{}\mathrm{K}$, and at elevated temperatures 160 °C and 180 °C) where the ${}_{}{}^{36}{}_{}{}^{}\mathrm{K}$ is oriented through a combination of direct optical pumping and spin exchange. The fraction of the maximal nuclear alignment for the 180 °C data was determined to be 0.46±0.07 stat±0.05 syst through measurements of the γ-ray anisotropy following positron decay. Roughly ${10}^5$ or more decays of oriented ${}_{}{}^{36}{}_{}{}^{}\mathrm{K}$ occurred each second. The application of the superallowed decay of ${}_{}{}^{36}{}_{}{}^{}\mathrm{K}$ to measurements of time-reversal symmetry in β decay is discussed.

• Received 29 September 1994

DOI:https://doi.org/10.1103/PhysRevC.52.R464