Mean Lifetimes of Levels inAl26

The mean lifetimes of levels in ${}_{}{}^{26}{}_{}{}^{}\mathrm{Al}$ below 4 MeV have been investigated with the Doppler-shift attenuation method and the ${}_{}{}^{24}{}_{}{}^{}\mathrm{Mg}({}_{}{}^3{}_{}{}^{}\mathrm{He},p){}_{}{}^{26}{}_{}{}^{}\mathrm{Al}$ reaction at 6 MeV. The outgoing protons have been detected at angles of ±60° with respect to the beam axis, in coincidence with $\gamma$ rays detected at 90° in an 80-${\mathrm{cm}}^3$ Ge(Li) detector. The results for levels below 3 MeV are generally in agreement with earlier lifetime studies. New information is reported for the following levels (energy in keV, lifetime in fsec): 2741 (54±8), 3074 (290±70), 3161 (36±10), 3597 (44±17), 3680 (27±12), 3721 (<23), 3750 (43±9), 3754 (27±11), and 3962 (68±14). The 3074-keV level is assigned positive parity on the basis of the present lifetime results. Experimental transition strengths are extracted and discussed in terms of isospin selection rules in electromagnetic transitions.