Level structure of 225Ac

The level scheme of 225Ac has been deduced from the study of the α-decay of 229Pa and β-decay of 225Ra. Sources of 229Pa were produced by the 229Th(d,2n) and 230Th(d,3n) reactions, and the 225Ra activity was obtained by milking a 229Th sample. Gamma singles spectra of 229Pa and 225Ra were measured with high-resolution Ge detectors placed in a very low background shield. Alpha-gamma and γγ-coincidence measurements were made with 229Pa sources. Using the ratio of the KX-ray and γ-ray intensities obtained from gated γ-ray spectra, we were able to deduce K conversion coefficients of the 115.55 and 120.80 keV transitions which gave M1 multipolarities for these transitions. Four bands were identified: Kπ = 3-/2, ground; 3+/2, 40.09 keV; 5-/2, 120.80 keV; and 5+/2, 155.65 keV. The half-life and alpha branching ratio, α/(α + EC), were measured to be 1.50 ± 0.05 d, and (0.48 ± 0.05)%, respectively. (orig.)