Microscopic Study of Superdeformed Rotational Bands in 151Tb

Structure of eight superdeformed bands in the nucleus 151Tb is analyzed using the results of the Hartree-Fock and Woods-Saxon cranking approaches. It is demonstrated that far going similarities between the two approaches exist and predictions related to the structure of rotational bands calculated within the two models are nearly parallel. An interpretation scenario for the structure of the superdeformed bands is presented and predictions related to the exit spins are made. Small but systematic discrepancies between experiment and theory, analyzed in terms of the dynamical moments, J(2), are shown to exist. The pairing correlations taken into account by using the particle-number-projection technique are shown to increase the disagreement. Sources of these systematic discrepancies are discussed -- they are most likely related to the yet not optimal parametrization of the nuclear interactions used.Comment: 32 RevTeX pages, 15 figures included, submitted to Physical Review

Time-odd components in the mean field of rotating superdeformed nuclei

Rotation-induced time-odd components in the nuclear mean field are analyzed using the Hartree-Fock cranking approach with effective interactions SIII, SkM*, and SkP. Identical dynamical moments ${{\cal J}^{(2)}}$ are obtained for pairs of superdeformed bands $^{151}$Tb(2)--$^{152}$Dy(1) and $^{150}$Gd(2)--$^{151}$Tb(1). The corresponding relative alignments strongly depend on which time-odd mean-field terms are taken into account in the Hartree-Fock equations.Comment: 23 pages, ReVTeX, 6 uuencoded postscript figures include

Extended investigation of superdeformed bands in 151,152^{151,152}Tb nuclei

A detailed study of known and new SD bands in Tb isotopes has been performed with the use of the EUROBALL IV -ray array. The high-statistics data set has allowed for the extension of known SD bands at low and high spins by new -ray transitions. These transitions, as it turns out, correspond to the rotational frequencies where the principal superdeformed gaps (Z=66,N=86) close giving rise to up- or down-bending mechanisms. This enables to attribute the underlying theoretical configurations with much higher confidence as compared to the previous identifications. Five new SD bands have been discovered, three of them assigned to the 152Tb and the two others to the 151Tb nuclei. Nuclear mean-field calculations have been used to interpret the structure of known SD bands as well as of the new ones in terms of nucleonic configurations

Enhanced population of superdeformation in the mass A = 150 region

Matière Nucléair

Degenerate superdeformed states in Gd150

The superdeformed (SD) structure of 150Gd has been studied using the Eurogam gamma-ray spectrometer and three new SD bands have been discovered. An interaction is observed between two of the SD bands caused by the near degeneracy of two levels. This is the first observation of accidental degeneracy between SD states. The interaction strength is determined to be 11 keV and evidence for crosstalk between the bands is observed. The absolute energy difference between two SD states in the second minimum has been accurately measured and the relative spins and parities of the two bands have been fixed

Selective studies of the excited rotational bands in the superdeformed nucleus 151^{151}Tb

The experimental study of the unresolved rotational bands, forming ridge structures in $\gamma-\gamma$ spectra, has been performed on the superdeformed nucleus $^{151}$Tb. $\gamma$ transitions from the reaction $^{27}$Al, at 155 MeV, on $^{130}$Te were measured with EUROBALL IV in high fold coincidence. The analysis of the intensities and count fluctuations of the ridge structures shows the existence of \approx 30 discrete rotational bands of superdeformed nature, half of which is in direct coincidence with the superdeformed yrast band. A comparison with band mixing model predictions and with a previous work on the superdeformed nucleus $^{143}$Eu is presented

Pair excitations and a proton band crossing in superdeformed Gd-150

An excited superdeformed (SD) band in 150 Gd is associated with a two-particle-two-hole proton excitation and provides the first evidence for collective proton pair excitations in a SD nucleus. This band is seen to exhibit a discontinuity in the γ-ray transition energies (backbending), which is interpreted as a band crossing associated with the alignment of a pair of N=6 protons. There is further evidence that this excited SD band decays into the yrast SD band