Several instances of anomalously low values of the B(E2;41+→21+)B(E2;21+→0gs+) ratio (B4/2)<1 have previously been observed in several nuclei among the highly neutron deficient W-Os-Pt isotopes with even numbers of neutrons and protons. The relatively large number of cases suggests a striking new phenomenon that currently has no theoretical explanation. A clue to its origin might be achieved by comparing the B4/2 ratios in even-even nuclei with the corresponding ratios of transition rates in neighboring odd-mass nuclei. However, until now only one case (Os169) has been observed with an unusually low corresponding B4/2 ratio, approximately 1σ below 1. Electromagnetic transition rates between excited states in the extremely neutron deficient nuclide Os167 were measured using 15 single-crystal germanium detectors from the jurogam 3 array coupled to the RITU gas-filled separator. The excited states of interest were populated via the Mo92(Kr78,2pn) fusion-evaporation reaction and studied by selecting the rare reaction channel via recoil-α-decay tagging. The lifetimes of low-lying states were measured using the recoil distance Doppler shift method with the APPA plunger device. From the measured lifetimes in the rotational-like band structure assigned to the νi13/2 yrast intruder configuration, the B(E2;17/2+→13/2+) and B(E2;21/2+→17/2+) values were deduced, resulting in the ratio B(E2;21/2+→17/2+)B(E2;17/2+→13/2+)=0.49(10). The results were compared with previous measurements in the Os isotopic chain and theoretical mean-field calculations, implying that the odd neutron valence particle has limited, if any, influence on the B4/2 values for this particular single-particle configuration.

The lifetimes of low-lying excited states below the 8+ seniority isomer were directly measured using fast timing detectors in the neutron-deficient isotopes 98,100Cd. This experiment was conducted with the DEcay SPECtroscopy (DESPEC) setup at GSI, where the ions of interest were produced via a fragmentation reaction and identified using the FRagment Separator (FRS) before being implanted in the AIDA active stopper system, and the γ rays emitted during the de-excitation of isomeric states were detected by the LaBr3 FATIMA Array. The newly deduced values for the reduced transition probabilities were compared with shell-model calculations using different interactions and effective charges. The results indicate that, while 98Cd aligns well with a seniority scheme description, in 100Cd the transition strengths among low-lying states are not fully reproduced, and the nature of these states remains an open problem within the present theoretical description. Ultimately, a key element in the description of this region, crucial for nuclear physics and astrophysics, appears to be the proton-neutron term of the nuclear effective interaction.

At a fundamental level, the interactions between protons and protons, protons and neutrons, and neutrons and neutrons are not identical. Such isospin nonconserving interactions emerge when comparing the excitation energy of analog states in T=1 triplet nuclei. Here, we extend such an analysis to the A=78, T=1 triplet system - the heaviest system for which such complete data exists - and find strong disagreement with contemporary theory. This was achieved by pioneering the technique of recoil-β-β tagging to identify excited states in Zr78. We also established a Zr78 half-life of 25-8+17 ms and extended the T=1 band in Y78 to Jπ=(10+).

We present the first measurement of the 47K(d, p gamma)48K transfer reaction, performed in inverse kinematics using a reaccelerated beam of 47K. The level scheme of 48K has been greatly extended, with nine new bound excited states identified and spectroscopic factors deduced. Uniquely, the 47K(d, p) reaction gives access to nuclear states that are sensitive to the interaction of protons and neutrons in the widely spaced 1s and fp orbitals, respectively. Detailed comparisons with SDPF-U and SDPF-MU shell-model calculations reveal a number of discrepancies between theory and experiment. Intriguingly, a systematic overestimation of spectroscopic factors and a poor reproduction of the energies for 1- states suggests that the mixing between the pi s11/2d43/2 and pi s21/2d33/2 proton configurations in 48K is not correctly described using current interactions, challenging our description of light nuclei around the N = 28 island of inversion.

The detection and localization of special nuclear materials and other actinides are important in various applications, including nuclear security and radioactive waste management. This system detects the neutrons and gamma rays emitted by actinide materials to localize the sources within a sample. The system's detectors are constructed from organic scintillator cells, enabling rapid detection. When combined with Neutron–Gamma Emission Tomography (NGET), the system allows for precise localization of neutron-emitting sources. This study investigates the attainable spatial resolution of the technique in relation to the dimensions of the individual detector cells, with both experimental measurements and simulations, aiming to optimize detector geometries for various applications and requirements.

In recent years, several cases of nuclei presenting the so-called "B-4/2 anomaly" have been observed in the neutron-deficient region close to Z = 50 and Z = 82. In the last region, the osmium isotopic chain is of particular interest, as three consecutive isotopes, 168,169,170Os, have shown the presence of this peculiar phenomenon. An experiment aimed at extending the study to Os-167 was performed at the Accelerator Laboratory of the University of Jyvaskyla, using a beam of 78Kr at 360 MeV impinging on a Mo-92 target. Lifetimes of several low-lying states were measured using the Recoil-Distance Doppler Shift method. The preliminary analysis and the study of the influence of unobserved feeders are discussed.

Besides the level scheme, absolute transition strengths between excited states yield fundamental information on nuclear structure and can be determined from level lifetimes. The recoil distance Doppler-shift (RDDS) technique is very valuable for the measurement of lifetimes in the picosecond range. During the last years, our group constructed several very compact plunger devices for RDDS experiments with 7-ray spectrometers coupled to charged particle detector arrays situated in the target chamber, and with dedicated setups for multinucleon transfer reactions where the plunger must be placed at the grazing angle of the reaction. Recent investigations have addressed the evolution of nuclear structure in neutron-deficient nuclei in the A = 170 mass region from yrast B(E2) values and are discussed in this article. For these investigations very small B-4/2 = B(E2; 4(1)(+) 2(1)(+) )/B(E2; 2(1)(+) 0(1)(+) ) ratios are of particular interest, which cannot be explained with standard collective models and which are not expected from the actual level schemes nor this far from closed shells. Here, we present our new work on W-168, Pt-172, and 176Pt, focus on this B(E2) anomaly, and include B(E2) values between higher yrast states for which experimental data have been sparse.

Lifetime measurements of low-lying excited states in the semimagic (N=50) nucleus Rh95 have been performed by means of the fast-timing technique. The experiment was carried out using γ-ray detector arrays consisting of LaBr3(Ce) scintillators and germanium detectors integrated into the DESPEC experimental setup commissioned for the Facility for Antiproton and Ion Research (fair) Phase-0, Darmstadt, Germany. The excited states in Rh95 were populated primarily via the β decays of Pd95 nuclei, produced in the projectile fragmentation of a 850 MeV/nucleon Xe124 beam impinging on a 4g/cm2Be9 target. The deduced electromagnetic E2 transition strengths for the γ-ray cascade within the multiplet structure depopulating from the isomeric Iπ=21/2+ state are found to exhibit strong deviations from predictions of standard shell model calculations which feature approximately conserved seniority symmetry. In particular, the observation of a strongly suppressed E2 strength for the 13/2+→9/2+ ground state transition cannot be explained by calculations employing standard interactions. This remarkable result may require revision of the nucleon-nucleon interactions employed in state-of-the-art theoretical model calculations, and might also point to the need for including three-body forces in the Hamiltonian.

The neutron-rich rare isotope 190W is discussed as a candidate for a prolate-oblate transitional nucleus with maximum γ-softness. The collectivity of this isotope is assessed for the first time by the measurement of the reduced E2 transition probability of its first 2+ state to the ground state. The experiment employed the FAst TIming Array (FATIMA), comprised of 36 LaBr3(Ce) scintillators, which was part of the DESPEC setup at GSI, Darmstadt. The 41+ and 21+ states of 190W were populated subsequently to the decay of its 127(12) μs isomeric Jπ=10− state. The mean lifetime of the 21+ state was determined to be τ=274(28) ps, which corresponds to a B(E2;21+→01+) value of 95(10) W.u. The results motivated a revision of previous calculations within an energy-density functional-based interacting boson model-2 approach, yielding E2 transition properties and spectroscopic quadrupole moments for tungsten isotopes. From comparison to theory, the new data suggest that 190W is at the transition from prolate to oblate structure along the W isotopic chain, which had previously been discussed as a nuclear shape-phase transition.

In the last two decades, several unique phenomena in triaxially deformed nuclei, such as chiral doublet bands and wobbling motion have been revealed. Up to now, there are still many open questions which require further experimental and theoretical studies. To explore the collective motion in 131Ba, an experiment was performed using the XTU Tandem accelerator in the Legnaro laboratory, Italy. High-spin states of 131Ba have been populated via the heavy-ion fusion-evaporation 122Sn(13C, 4n) reaction. g-rays, charged particles and neutrons emitted from the residues were detected by the GALILEO array, EUCLIDES silicon ball, and the Neutron Wall, respectively. A total of 1.2 ×109 triple- or higher-fold events were collected by the GALILEO data acquisition system. The g-g-g coincidence events were sorted into a three-dimensional histogram (cube) and the analysis was carried out with the RADWARE and GASPWARE software packages. Through analysis of the coincidences between g-rays, the most comprehensive level schemes of 131Ba to date was deduced from the present work. The extended level-scheme consists of 15 rotational bands, and newly observed transitions are marked in red. Three nearly degenerate pairs of doublet bands (Band 3–8) are identified in 131Ba. Two pairs of chiral doublets (Band 3–6) with configuration πh11/2(g7/2,d5/2)×νh11/2 are interpreted as a set of pseudospin-chiral quartet bands. The quartet bands are fed by another pair of chiral doublet bands (Band 7–8) built on a πh211/2×νh11/2 configuration via a series of enhanced E1 transitions. We extracted the energy displacement δE and the B(E1)/B(E2) branching ratios between the positive-parity band 3 and the negative-parity band 7 in 131Ba and in comparison with those in 124Ba, 224Th, 133Ce and 135Nd. The energy displacement δE and the B(E1)/B(E2) branching ratios in 131Ba are comparable with those in 124Ba but deviate appreciably from those in 224Th which has been reported to have stable octupole deformation. The results indicate the existence of octupole correlations in 131Ba without stable octupole deformation. A new rotational band (Band 10) discovered in the low-spin region exhibits a level structure similar to a wobbling band. Assuming it as a wobbling band, the wobbling frequency was extracted and compared with other reported wobbling bands in the neighboring nuclei. The wobbling frequency of this band decreases with increasing angular momentum, and even exhibits negative value at the highest spin. Considering that the wobbling phonon should contribute a positive amount to the excitation energy, this band is unlikely to be explained by this mechanism. The band may originate from other collective excitation mechanisms such as g vibration. The newly identified rotational band (Band 9) composed of M1 transitions is tentatively assigned as a magnetic rotational band through a systematic analysis of the level structure. Finally, the configurations of other 4 bands, Band 12-15, are also suggested based on previous researches and the extracted quasiparticle alignments.