Excitation energies, spins, and nuclear lifetimes have been measured in ${}_{}{}^{28}{}_{}{}^{}\mathrm{Mg}$ by employing the reaction ${}_{}{}^{26}{}_{}{}^{}\mathrm{Mg}(t, p\gamma ){}_{}{}^{28}{}_{}{}^{}\mathrm{Mg}$ at bombarding energies in the neighborhood of 2.9 MeV. Reaction-produced protons were detected in an annular Si counter at an average angle of 171°, and coincident-$\gamma$-ray spectra were obtained with both NaI(Tl) and Ge(Li) detectors at angles $120°\ge \theta \ge 0°$ $\gamma$-ray angular distributions were extracted from data obtained with the NaI(Tl) detectors, while precision $\gamma$-ray energies and Doppler-shift attenuations were extracted from the data collected with the Ge(Li) detector. The results obtained for excitation energies (keV), spins, and lifetimes (psec) are: 1473.8±0.4, 2, 1.60±0.20; 3862.9±0.7, 0, 1 or 2, 0.75±0.10; 4021.2±1.6, 4, 0.21±0.07; 4557.4±0.8, 2, <0.04; 4877±4, 2, <0.18; 5171.6±0.8, 3, 0.10±0.07; 5190.7±3.0, 1, <0.03; 5470.5±5, 2, undetermined. $\gamma$-ray branching ratios and multipole-mixing ratios were also obtained from the data, and reduced electromagnetic transition matrix elements have been extracted for all transitions observed. The results are compared with the predictions of both the triaxial rotor model of Kurath and the shell-model calculations of de Voigt and Wildenthal.

• Received 19 December 1972

DOI:https://doi.org/10.1103/PhysRevC.7.1878