Investigation of A=155 and A=151 nuclides: Identification of the Tm155 s1/2 isomer and of the Yb155 decay branch

The decay properties of Lu155, Yb155, Tm155, and of the decay daughters Er151 and Ho151 were investigated following the on-line mass separation of A=155 nuclides produced in Zn64 irradiations of Mo95. In the study, the half-life of the low-spin isomer in Lu155 was measured to be 14020 ms, the decay branch of Yb155 was identified by observing daughter rays and Tm K x rays, and the existence in Tm155 of an s1/2 isomer (T1/2=444 s), in addition to the h11/2 ground state (T1/2=21.60.2 s) was established. Schemes for the decays of Yb155, Tm155, and Er151 are proposed. New information on Er151 decay establishes the s1/2 isomer in Ho151 to be 41.10.2 keV above the h11/2 ground state. Also, branchings of 905, 287, and 80-20+15% were determined for the decays of Yb155, Ho151, and Hom151, respectively.