High spin states inLu164

Abstract

High spin states in the odd-odd 164 Lu nucleus have been investigated for the first time, through in-beam gamma-ray spectroscopy, following the 150 Sm͑ 19 F,5n͒ reaction at beam energy E lab ϭ105 MeV. Four bands, including two signature split bands are identified. The interpretation of the experimental results is discussed in comparison with the existing data in the neighboring nuclei and in the framework of the cranked shell model. The h 11/2 i 13/2 yrast band exhibits anomalous signature splitting and signature inversion is observed at a spin of 18ប. This provides the missing datum for the systematics of staggering and signature inversion for the neighboring odd-odd Nϭ93 isotones and supports the predictions of angular-momentum projection calculations by Hara and Sun. In the second signature split h 11/2 h 9/2 band, the AB neutron crossing occurs at a rotational frequency of ϳ0.29 MeV. This is indicative of the disappearance of the blocking effect of the odd neutron.

High-Spin States in Odd–Odd168Lu

“…2) Together with the identical bands in 171{175 Ta (Z ¼ 73), 1) such rare cases of identical bands between odd-Z and odd-odd isotopes are quite contrasting to the usual cases observed between odd-Z and even-even isotones at both normal deformation and superdeformation. 6,7) For a band of h 11=2 coupled to h 9=2 in a lighter 164 Lu nucleus, 3,4) the neutron AB band crossing was observed to be unusually delayed in comparison with neighboring nuclei. The two cases of the band built upon g 7=2 or h 11=2 coupled to h 9=2 have been known to have this anomalous band crossing to date.…”

“…On the experimental side, spectroscopic data for their high-spin states should be available as the oddodd Lu isotopes are considered as good candidates. Previous high-spin studies were reported on 160 Lu, 10) 162 Lu, 11) 164 Lu, 3,4) 166 Lu 12) and 170 Lu. 13) However, high-spin studies on 168 Lu were completely absent until our short report was published.…”

“…In particular, the latter has been conceived as an important ingredient underlying several intriguing phenomena such as the identical band problem, 1,2) anomalous (delayed) band crossing 3,4) and signature inversion. 5) Recent experimental investigations in this mass region have mainly been focused on these three phenomena and such good examples are found in numerous high-spin states of odd-odd nuclei spanning Eu, Tb, Ho, Tm, Lu and Ta.…”