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Connections between the superdeformed and normaldeformed states in 143Eu have been established by measuring energy sums of two consecutive γ-ray transitions in the linking cascade. Six decay paths have been observed connecting discrete states in the two potential wells. The absolute excitation energy and the most likely spin of a superdeformed band have been determined directly for the first time.

The strongly shape driving ph9/2[541]l/2- configuration with a=+1/2 exhibits some anomalous, and so far unexplained, features concerning the crossing frequency, h?c, the aligned angular momentum, ix, and interaction strength, at the alignment of the first pair of i13/2 quasineutrons in several odd-Z rare earth-nuclei. The h9/2[541]1/2- and h11/2[523]7/2- bands have been studied in the stably deformed rare-earth nucleus163Tm to investigate these features. A difference in band crossing frequency of ~ 80 keV between the two bands is found. Rotational bands built on these two configurations have been found to cross in the spin range I=25/2–29/2 h. The?-decay pattern between the two bands is established in the crossing region and analysed in terms of a moderate shape difference between them. A theoretical estimate of the size of the interaction strength between the two bands is presented and compared to the experimental value. The observed band structure in163Tm is very similar to that of167Lu which has 2 protons and 2 neutrons in addition. This observation is discussed in relation to the similarity of the yrast bands of the two even-even “core” nuclei162Er and166Yb, for which the?-transition energies are identical within ~0.2 keV below the vi13/2 crossing.

Rotational bands in the odd-proton nucleus 171Lu have been populated with the 160Gd(19F, α4n) reaction. High-spin states were observed to a maximum spin of 732− using the NORD-BALL array. Several new three-quasiparticle bands were observed, including one based on the π12−[541]⊗ν72+[633]⊗ν12−[521] configuration. The signature splitting of this band is inverted from the expected splitting, and this is interpreted as being due to a residual proton-neutron interaction. The contribution of this interaction to the increased crossing frequency observed for the alignment of i132 neutrons in the π12−[541] band is considered. Strong E1 transitions from high-spin levels in the π12+[411] band to the π12−[541] band are observed.

The level scheme of143Eu has been extended to I=75/2 in an experiment with the NORDBALL Compton-suppressed Ge detector array and the110Pd(37Cl, 4n) reaction. Most of the scheme shows irregular structure of multiparticle excitations. A strongly populated straight cascade of more than 10 stretched E2 transitions suggests the onset of collectivity.