α decay of 217Th populating excited states in 213Ra -: art. no. 034309

We have observed the cu decay of Th-217 populating the low-lying two excited states in Ra-213. The branching ratio to the first and the second excited states in Ra-213, which have expected J(pi) values of 5(-)/2 and 3(-)/2,was determined to be 2.6(-1.1)(+1.6) % and 5.1(-1.6)(+2.0) %, respectively, and the energy of the second excited state in Ra-213 was determined to be 834 keV for the first time. The systematical trend of the branching ratio for N=125 isotones with even proton numbers near the Pb-208 core was reasonably explained by the shell model of a decay, where the relative reduced width for specific neutron-orbital and angular momentum has an identical value for the nuclei in the systematics.