Level structure of 225Ac

Abstract The level scheme of 225 Ac has been deduced from the study of the α-decay of 229 Pa and β − decay of 225 Ra. Sources of 229 Pa were produced by the 229 Th(d, 2n) and 230 Th(d, 3n) reactions, and the 225 Ra activity was obtained by milking a 229 Th sample. Gamma singles spectra of 229 Pa and 225 Ra were measured with high-resolution Ge detectors placed in a very low background shield. Alpha-gamma and γγ-coincidence measurements were made with 229 Pa 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: K π = 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.