A rotational band of nineteen transitions with a moment of inertia 3$ nA of 84£ 2 MeV" 1 has been observed in 152 Dy. The band feeds into the oblate yrast states between 19" and 25" and it is proposed that the lowest member of the band has a spin of 22 + and thus the band extends up to 6Qfr. It is identified as the yrast superdeformed band and its intensity accounts for the whole of the ridge structure seen previously in continuum E y -E r correlations.PACS numbers: 21.10. Re, 23.20.Lv, 27.70.+q The nucleusDy has been extensively studied and three different structures have been identified. The low-spin yrast levels have a pseudovibrational structure 1 which develops into a low-deformation (fi = 0.15) prolate rotational band 2 extending up to 40fr. This band, in the spin region between SR and 38£, lies between 0.5 and 1.5 MeV above the yrast states which have a weak oblate structure formed by particles in equatorial orbits. 3 " 5 At higher spins the y-ray continuum is dominated by a collective E2 bump. 6 Part of this bump has been shown to arise from superdeformed (/J^O^) bands from the existence of ridges with a moment of inertia3 (2) = (85 ±2)H 2 MeV" 1 in E y 'Ey correlation spectra. 7,8 In this Letter we present data showing a discrete-line rotational band extending over nineteen transitions from 602 to 1449 keV with an almost constant energy separation of 47 keV which corresponds to the superdeformed moment of inertia. The major -y-ray decay deexciting the band feeds into the yrast oblate structure between the 19"" and 25"" states and then proceeds via the 60-ns 17 + isomer. Additionally 25% of the decay intensity bypasses this isomer. We propose that the decay process from the bottom of the band is essentially statistical, involving several transitions, and we assign the spin at the bottom of the band to be 22£, thus establishing the spin at the top of the band to be 60fr. This is the first observation of a discrete-line superdeformed band and it extends the spin at which discrete states have been seen from about 46* (e.g., 158 Er, Tj0m etaL 9 ) to 60T.The experiment was carried out on the tandem accelerator at the Daresbury Laboratory using the TES-SAS spectrometer, which consists of a 50-element bismuth germanate (BGO) crystal ball similar to that used in TESSA2 10 with twelve escape-suppressed germanium detectors. 11 The states in 152 Dy were populated by the reaction 108 Pd( 48 Ca,4>7) at 205 MeV with a target consisting of two 500-/ig-cm~2 self-supporting foils isotopically enriched at 95% in 108 Pd. A 15-mgcm" 2 gold catcher foil was positioned 5 cm downstream of the targets such that it was outside the focus of the germanium detectors but within the full detection efficiency of the BGO ball. A total of over 150 million double (Ge-Ge) coincidences were recorded together with the sum energy and number of hits (fold) in the BGO ball. The time difference between the BGO ball and the second-coincidence germanium detector was recorded and enabled most of the neutron-induced events in the germanium detec...

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The structure of recently discovered identical superdeformed bands in |S| Tb and ,52 Dy and in l50 Gd and 15, Tb are discussed in terms of the strong-coupling approach. Based on the experimental evidence that the superdeformed core of ,52 Dy is extremely insensitive to the polarization effects induced by the odd particle, the bands are shown to exhibit the presence of the pseudo SU(3) symmetry at extreme conditions of large elongations and high spins.