Decay properties of Yb153 and Tm153; Excitation energies of the s1/2 and h11/2 proton states in Tm153

The decay properties of Yb153 and Tm153, produced in Zn64 bombardments of Mo92, were investigated following on-line mass separation. A decay scheme, incorporating 34 transitions and 25 levels in Tm153, was constructed for Yb153. It establishes the s1/2 proton level in Tm153 to be isomeric at an excitation energy of 43.2 keV. The ±-decay branch of the h11/2 Tm153 ground state was determined to be 91±3%. In addition, a partial decay scheme was put together for the 9% + branch. About 66% of this + decay proceeds to the h9/2 neutron state located at 299.3 keV in Er153. Only one transition, 266.5 keV, could be assigned to the + decay of the Tm153 s1/2 isomer; it is suggested that the ray deexcites the p3/2 neutron level to the f7/2 Er153 ground state. Based on the intensity of this 266.5-keV ray, the isomers ± branch was estimated to be 1/493%.