Levels in 227Ac populated in the 230Th(p,α) reaction

The 230,232Th(p,α)227,229Ac reactions were studied using 20 MeV protons and a magnetic spectrograph to analyze the reaction products. Relative populations of levels in 229Ac correlated well with previously published (t,α) results for the same final levels, showing that the similarity of the two reactions observed empirically in the deformed rare earth region extends to actinides. The most strongly populated level in 227Ac is at 639 keV, and is assigned as the 1/2+[400] bandhead. The 435 keV level, previously adopted as the 1/2+[660] bandhead, also has a significant intensity that is attributed to ΔN=2 mixing between these two K=1/2 proton orbitals. The ΔN=2 matrix element estimated from these data is ∼80 keV, similar to values observed for the same two Nilsson states as neutron orbitals in the dysprosium isotopes.