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Prolate-oblate shape coexistence close to the ground state in the strongly-deformed proton-rich A≈120 nuclei is reported for the first time. One of the four reported bands in $^{119}$Cs, built on a 11/2− state at 670 keV, consists of nearly degenerate signature partners, and has properties which unequivocally indicate the strongly-coupled πh11/2[505]11/2− configuration associated with oblate shape. Together with the decoupled πh11/2[541]3/2− band built on the 11/2− prolate state at 110 keV, for which a half-life of T1/2=55(5)μs has been measured, the new bands bring evidence of shape coexistence at low spin in the proton-rich strongly deformed A≈120 nuclei, a phenomenon predicted since long time, but not yet observed. Calculations using the particle-number conserving cranked shell model and two dimensional tilted axis cranking covariant density functional theory support and well reproduce the observed oblate and prolate coexisting low-energy states in $^{119}$Cs.

Two newly observed bands built on a two-quasiparticle configuration in $^{130}$Ba have been investigated for the first time with the microscopic projected shell model. The experimental energy spectra and the available electromagnetic transition probabilities are well reproduced. The wobbling character of the higher band is revealed by the angular momentum projected wavefunctions via the K plot and the azimuthal plot. This provides the first strong microscopic evidence for wobbling motion based on a two-quasiparticle configuration in even-even nuclei.

International audience; The g factor of the 56 ns half-life isomeric state in $^{128}$Cs has been measured using the time-differential perturbed angular distribution method. This state is the bandhead of the positive-parity chiral rotational band, which emerges when an unpaired proton, an unpaired neutron hole, and an even-even core are coupled such that their angular momentum vectors are aplanar (chiral configuration). g-factor measurements can give important information on the relative orientation of the three angular momentum vectors. The measured g factor g=+0.59(1) shows that there is an important contribution of the core rotation in the total angular momentum of the isomeric state. Moreover, a quantitative theoretical analysis supports the conclusion that the three angular momentum vectors lie almost in one plane, which suggests that the chiral configuration in $^{128}$Cs demonstrated in previous works by characteristic patterns of electromagnetic transitions appears only above some value of the total nuclear spin.

Medium and high-spin states in Ce133 were investigated using the Cd116(Ne22, 5n) reaction and the Gammasphere array. The level scheme was extended up to an excitation energy of ∼22.8 MeV and spin 93/2. Eleven bands of quadrupole transitions and two new dipole bands are identified. The connections to low-lying states of the previously known, high-spin triaxial bands were firmly established, thus fixing the excitation energy and, in many cases, the spin parity of the levels. Based on comparisons with cranked Nilsson-Strutinsky calculations and tilted axis cranking covariant density functional theory, it is shown that all observed bands are characterized by pronounced triaxiality. Competing multiquasiparticle configurations are found to contribute to a rich variety of collective phenomena in this nucleus.

The nature of the chiral candidate bands in ¹06Ag, one of only two known examples of candidates which actually cross, is investigated experimentally and theoretically. Lifetimes have been determined for these bands in ¹06Ag using the Doppler-shift attenuation method with the g-detector array AFRODITE. The level scheme of ¹06Ag has been extended, and three negative-parity bands have been observed to high spins. Configurations were assigned to the negative-parity bands based on a quasiparticle alignment analysis and on configuration-fixed constrained relativistic mean field calculations. The excitation energies, B(M1) and B(E2) values, as well as B(M1)/B(E2) ratios have been compared with results of particle-rotor model calculations. From the investigations, it is concluded that the three close-lying negative-parity bands are a two-quasiparticle high-K band and a pair of four-quasiparticle bands. The proposal that the two lowest-lying bands are chiral partners has not been confirmed.

Two distinct sets of chiral-partner bands have been identified in the nucleus Ce133. They constitute a multiple chiral doublet, a phenomenon predicted by relativistic mean field (RMF) calculations and observed experimentally here for the first time. The properties of these chiral bands are in good agreement with results of calculations based on a combination of the constrained triaxial RMF theory and the particle-rotor model.

The structure of 58Fe was investigated at Gammasphere using 48Ca(13 ,14C,xn) fusion-evaporation reactions at a beam energy of 130 MeV. The level scheme has been revised and extended to J∼17 and an excitation energy of 16.6 MeV. Regular band structures consisting of low-energy ΔJ=1 transitions have been observed at moderate spin (J∼8-15) and are candidates for magnetic rotational bands. Self-consistent tilted-axis-cranking calculations within a relativistic mean-field theory were applied to investigate these bands and were found to reproduce the experimental results well. In other parts of the level scheme, quasirotational bands composed of stretched-E2 transitions have been extended to high spin, and other new bands have been identified. Positive-parity experimental states were compared to predictions of the spherical shell model using the GXPF1A, KB3G, and FPD6 effective interactions in the fp model space. The projected shell model, with a deformed quasiparticle basis including the neutron νg9/2 orbital, was applied to interpret regular ΔJ=2 band structures that extend beyond the maximum spin available for π[(f7/2)-2]- ν[(p3/2f 5/2p1/2)4] configurations and exhibit features characteristic of rotational alignment. It is clear that the νg9/2 intruder orbital plays a crucial role in describing the quasirotational structures in this nucleus, even starting as low as J∼5.