First identification of high spin states in160Lu

Abstract

High spin states of odd-odd transitional nuolei are not especially wen studied because of the complexity of the level schemes, even though of considerable interest, particularly as candidates for the appearance of larger delay in crossing frequency, or signature inversion. In the present work, the high spin states of xr'~ were identified for the first time in the 1448m(XgF,3n)l~u fusion-evaporation reaction with a beam of 90 MeV provided by the HI-13 tandem accelerator of China Institute of Atomic Energy(CIAE). In order to identify the de-exciting gamma rays of different reaction residuals and choice of the best energy of the 19F bt~ql, exeitatiort furtotiom and the residual radioactivity were measured for the bombarding energy range from 85 to 105 MeV. The u ooinoidenc~ expemnent was pea'formed using five HpGe-BGO Compton-suppre~,xl spectrometers plaoed at 15-20 em from the target and a 14 elements ball of BGO detectors. A metallic 144Sm target with an evaporated lead backing of 1.0 mg/em 2 was used. The target material was isotopicaUy enriched to 88.6% and rolled to a thickness of about 2 mg/em 2. A total of about 106 events, each with at least two Compton-suppressed HpOe detectors and one BGO detector to be in coincidence, were recorded on magnetic tapes in event-by-event mode for off-line analysis.The most strongly populated rotational band observed in the present work is presented in figure 1 and a sample of coincidence-spectra gated by 248 keV is shown in figure 2. The Nilsson configuration of this band in l@Lu is assigned as n9/2-[514]| This assignment is consistent with the systematies that exists for the neighboring isotopes and other odd-odd nuclei [I,2]. As this basis we assttmed K=5 for the band. From an analysis