High-spin states in odd-odd Lu-168

Abstract

We observed four rotational bands in Lu-168 using the Tb-159(C-13,4ngamma)Lu-168 reaction at 58.5 MeV and 62 MeV and populated high spin states up to 27 h. On the basis of the X-gamma gating procedure and excitation function measurements done at beam energies of 50, 55, 58.5, 60, 62 and 64MeV, we could identify the gamma-ray transitions belonging to Lu-168. The configurations of two strongly populated rotational bands (bands A and B) were based on, our previous study and were examined by using the additivity relation for alignments. The configurations of two newly found rotational bands (bands C and D) were also assigned by the additivity relation. These identified configurations were confirmed by the Drissi's recipe and energy systematics of neighboring odd-odd nuclei. The configuration of bands A was assigned as K-pi = 6(+)[pi7/2(+)[404] + v5/2(+)[642]]. The configurations of the previous reported band B and two new bands C and D are likely to be 3(-)[pi1/2(-)[541] + v5/2(+)[642]], 7(-)[pi9/2(-)[514] + v5/2(+)[642]] and 5(+)[pi5/2(+)[402] + v5/2(+)[642]], respectively. We observed band crossing for three bands A, C and D, but not for band B. The extracted band crossing frequencies were consistent with the neutron BC crossing observed in neighboring odd-odd nuclei as well as odd-N and even-Z nuclei in this mass region. This was attributed to the occupied v5/2(+)[642] Nilsson configuration arising from the neutron vi(13/2) orbital. Energy systematics of bands built on pig(7/2) circle times vi(13/2) and pih(11/2) circle times vi(13/2) in neighboring odd-odd nuclei were also studied in comparison with bands A and C in Lu-168.