Level structure of Ho-154

The excited states of the odd-odd Ho-154 nucleus have been studied by using in-beam gamma-ray spectroscopy with the Pr-141 (O-16, 3n) Ho-154 reaction at E-lab = 75 MeV. The beam was provided by the 12UD Pelletron accelerator at the University of Tsukuba. In this work, the complicated decay pattern of low energy transitions just above the T-1/2 = 3.10 min isomer have been established. In addition, a number of new states and gamma-ray transitions, especially those associated with energetically favored band termination, have been observed for the first time in Ho-154. A negative collective band and its signature partner built on the 11(-) level are interpreted as being based on the pi h(11/2) circle times vi(13/2) configuration. A positive band built on the 10(+) level is based on the pi h(11/2) circle times vh(9/2) configuration while another positive band built on the 9(+) level is being associated with the pi h(11/2) circle times vf(7/2) configuration. An energetically favored level J(pi) = 19(-) can be interpreted as being attributed to the pi h(11/2) circle times vi(13/2) configuration coupled to the 8(+) state in neighboring core Dy-152, namely, a four-quasiparticle alignment based on the [pi h(11/2) circle times vi(13/2)](11-) circle times[v(h(9/2)f(7/2))](8-) configuration. Another energetically favored state at J(pi) = 27(-) is assigned the six-quasiparticle [pi(h(11/2))(3)](27/2-)circle times[v(f(7/2)h(9/2)i(13/2))](27/2-) configuration.