Low-lying states in the isotope 130 Xe were populated in a Coulomb-excitation experiment performed at CERN's HIE-ISOLDE facility. The magnitudes and relative signs of seven E 2 matrix elements and one M1 matrix element coupling five low-lying states in 130 Xe were determined using the semiclassical coupled-channel Coulomb-excitation least-squares search code GOSIA. The diagonal E 2 matrix elements of both the 2 + 1 and 4 + 1 states were extracted for the first time. The reduced transition strengths are in line with those obtained from previous measurements. Experimental results were compared with the general Bohr Hamiltonian with the microscopic input from mean-field theory utilizing universal nuclear energy density functional (UNEDF0), shell-model calculations using the GCN50:82 and SN100PN interactions, and simple phenomenological models (Davydov-Filippov and γ-soft). The extracted shape parameters indicate triaxial-prolate deformation in the ground-state band. In general, good agreement between theoretical predictions and experimental values was found, while neither phenomenological model was found to provide an adequate description of 130 Xe.

Background: The γ softness of 136 Nd makes it possible to study the shape changes induced by two-proton or two-neutron excitation. Purpose: We measure the lifetimes of two-quasiparticle states of the bands based on the 10 + states at 3296 and 3279 keV to investigate the shape change induced by the alignment of two protons or two neutrons in the h 11/2 orbital. Methods: The recoil-distance Doppler shift method was used for the study of 136 Nd studies, which was formed by the fusion reaction 120 Sn(20 Ne, 4n) 136 Nd, at E beam = 85 MeV. Calculations were performed within the microscopic-macroscopic approach, based on the deformed Woods-Saxon single-particle potential and the Yukawa-plus-exponential macroscopic energy. Results: The lifetime of the 10 + state at 3279 keV of 136 Nd was measured to be T 10 + 1/2 = 1.63(9) ns. The lifetimes of the 2 + state at 374 keV and of the 12 + state at 3686 keV of the ground band were also measured to be T 2 + 1/2 = 26.5(14) ps and T 12 + 1/2 = 22.5(14) ps. Conclusions: The measured lifetime of 10 + the state at 3279 keV together with other observables confirm the structure change in 136 Nd. A rather small reduced hindrance of the electromagnetic decay of the 10 + state at 3279 keV would be consistent with its K-mixed character.

The properties of the K-isomer decays in the 134 Nd and 184 Pt nuclei have been investigated. Measurements were carried out in e-γ and γ-γ coincidence modes using electron spectrometers coupled to the central European Array for Gamma Levels Evaluations at the Heavy Ion Laboratory of the University of Warsaw. Internal conversion coefficients were obtained for transitions relevant to the decay of the isomeric states, allowing the determination of multipolarities and mixing ratios as well as hindrance factors. Two possible causes of the weakening of the K forbiddenness, namely rotational K mixing (Coriolis interaction) and triaxiality, are briefly discussed using schematic theoretical models.

Background: Investigation of the 140 62 Sm 78 nucleus, situated in the area close to the magic N = 82 neutron shell, offers the opportunity to find and study interesting phenomena resulting from the interplay of collective and other degrees of freedom. Purpose: Experimental identification of low-spin low-energy levels, particularly 0 + , in 140 Sm and theoretical interpretation within the collective general Bohr Hamiltonian (GBH) model. Method: The γ -γ angular correlation technique for γ radiation after the β/EC decay of 140 Eu → 140 Sm and 140 Gd → 140 Eu → 140 Sm was used to determine spins of excited states of 140 Sm. The 140 Gd and 140 Eu nuclei were produced in the 104 Pd + 40 Ar reaction at the HIL UW cyclotron. In the theoretical part the full five-dimensional GBH model was applied in two variants: the simple phenomenological Warsaw model and the microscopic version with six inertial functions and a potential calculated from mean-field theory. Results:The spin and parity of six low spin (0,1,2) low lying excited levels of 140 Sm were measured. Two new states at around 2 MeV were identified. A analysis of the consequences of possible admixtures on the determination of the spin of a level was performed. The theoretical models applied successfully describe most of the spectrum of 140 Sm giving hints on the origin of the states observed in the experiment. Conclusions: Significant softness against nonaxial deformation seems to be essential to interpret the properties of 140 Sm. Further experimental studies are needed to check if some low-energy excitations are not deformation driven.