No 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.

An experimental investigation of the odd-odd 162 Lu nucleus, following the 148 Sm( 19 F,5n) reaction at beam energy E lab ϭ112 MeV, has been performed through in-beam gamma-ray spectroscopy. It revealed three signature-split bands. The yrast band based on h 11/2 i 13/2 configuration exhibits anomalous signature splitting ͑the unfavored signature Routhian lying lower than the favored one͒ whose magnitude ⌬eЈϷ25 keV, is considerably reduced in contrast to sizable normal signature splitting ⌬eЈϷ125 and 60 keV observed in the yrast h 11/2 bands of the neighboring odd-A 161,163 Lu nuclei, respectively. The signature inversion in this band occurs at spin ϳ20ប (frequencyϭ0.37 MeV). The second signature-split band, observed above the band crossing associated with the alignment of a pair of i 13/2 quasineutrons, is a band based on the four-quasiparticle ͓h 11/2 ͓523͔7/2 Ϫ h 9/2 ͓521͔3/2 Ϫ (i 13/2 ) 2 ͔, i.e., EABA p (B p ), configuration. The third signature-split band is also likely to be a four-quasiparticle band with configuration similar to the second band but involving F quasineutron, i.e., FABA p (B p ). The experimental results are discussed in comparison with the existing data in the neighboring nuclei and in the framework of the cranking shell model. ͓S0556-2813͑97͒01809-8͔