Search

Bent Herskind was a Gamma-Ray Grand Master, who helped trigger the modern revolution in γ -ray spectroscopy, opening the door to new vistas in nuclear structure physics. His story is a remarkable one and the contributions he made to the field in terms of its scientific richness and to the development of ever more powerful detector systems, were unique. The enthusiasm and excitement he put into everything were infectious and the brilliance of his insights was compelling. His legacy will live on, not only in the significant discoveries that he made, but also in the way he instilled his deep commitment to unravelling nature’s secrets in this quest and the pleasure of physics discovery with his close collaborators. This review article summarises his career and highlights some of his scientific achievements in which the authors had the privilege to collaborate with him. [ABSTRACT FROM AUTHOR]

The attention to the contaminants of emerging concerns or micropollutants is continuously rising, also stimulated by the new initiatives at European level. The present study focuses on the removal of target micropollutants in a conventional activated sludge wastewater treatment plant which is the most common system and considered a source of micropollutants to the environment. The aims were to evaluate the removal efficiency of different stages of the wastewater treatment plant and to conduct the Environmental Risk Assessment on the final effluent. As indicated by the European's guidelines on Environmental Risk Assessment, the SimpleTreat4.1 model was applied to this purpose: different values of the biodegradation constant, which represents the key factor for modelling, were applied, and the effects on the quality of prediction were evaluated. The evaluations were carried out thorough 3-year monitoring activity in a full-scale wastewater treatment plant on 10 micropollutants belonging to the classes of illicit drugs, pharmaceuticals and psychoactive. The model was found statistically not satisfactory for most of the investigated micropollutants. A better prediction was obtained when the biodegradation constant was calculated based on the full-scale data. Nonetheless, the results obtained in terms of risk were considered acceptable and comparable among each other. [ABSTRACT FROM AUTHOR]

The paper reviews the searches for shape isomers, which are "extreme" example of shape-coexistence phenomena in nuclei. They may appear when highly deformed structures, well localized in the nuclear Potential Energy Surface (PES) in the deformation space, undergo a significant change in shape to match the final state shape, thus leading to a substantially hindered γ decay. This is in sharp contrast to the vast majority of shape-coexistence phenomena, where significant mixing in the initial and final state wave functions is found. So far, the most spectacular examples of shape isomerism are known in fissioning systems in the actinides, although only scarce experimental information is available from experiments conducted more than 20 years ago. Searches in lighter mass regions, guided by theory predictions based on different approaches and experimental investigations on superdeformed systems, are also presented. They point to 64 , 66 Ni as additional examples of prolate deformed shape-isomer-like structures, although with much reduced hindrance with respect to the actinides. Their origin is strictly related to the action of the monopole component of the tensor force of the nucleon-nucleon interaction, which is expected to favor the appearance of deep secondary minima also in the PES of Sn nuclei with masses 112–118. Perspectives in current searches of shape isomerism with modern detection systems, in the actinides regions and in lighter masses, are discussed. [ABSTRACT FROM AUTHOR]

Multi-Nucleon Transfer (MNT) reactions have been used for decades as a reaction mechanism, in order to populate excited states in nuclei far from stability and to perform nuclear structure studies. Nevertheless, the development of set-ups involving high acceptance tracking magnetic spectrometers (mainly existing in Europe), coupled with the Advanced GAmma Tracking Array (AGATA) opens new possibilities, especially if they are used in conjunction with high-intensity stable beams or ISOL RIBs. In this article, we will discuss the capabilities of such set-ups aiming at different goals, including complete information in high-resolution spectroscopy as well as lifetime measurements. [ABSTRACT FROM AUTHOR]

The Advanced GAmma Tracking Array (AGATA) is a European project involving over 40 institutes in 12 countries. It aims to develop and operate a high-resolution gamma-ray tracking spectrometer. AGATA uses segmented germanium detectors and tracking algorithms to accurately determine the energy, time, and position of gamma-ray interactions. The project has completed several science campaigns and is now entering the next phase to realize a 180-detector array. AGATA's goals include studying nuclear structure, shell evolution, reaction dynamics, and astrophysical reactions. [Extracted from the article]

The paper reviews recent developments in γ -ray spectroscopy of the neutron-rich fragments produced in nuclear fission. This subject has been an intensive area of study spanning more than five decades. Here we highlight key results and describe the evolution of the associated experimental techniques since the last review papers in 1995 (I. Ahmad and W.R. Phillips, Rep. Prog. Phys. 58(11), 1415 (1995); J. H. Hamilton et al., Prog. Part. Nucl. Phys. 35, 635(1995)). Research themes in nuclear structure will be explored along with the fission reaction mechanism and the links to nuclear astrophysics and applications. [ABSTRACT FROM AUTHOR]

7Example of different TKEL conditions for 92 Mo using the shortest target-to-degrader distance. a Doppler-corrected spectrum without a TKEL condition. b Condition on the low part of the TKEL. c More restrictive condition on the low part of the TKEL. d Condition on the high part of the TKEL. 10Simulated Doppler corrected -ray spectra using the velocity from PRISMA (after the degrader) for 50 Ca showing the DSAM and RDDS techniques. The original article can be found online at https://doi.org/10.1140/epja/s10050-023-01027-2. [Extracted from the article]

We investigate the physical properties of compressed gray phosphorus through density functional plus dynamical mean-field theory, showing self-doping and s -wave electronic structure reconstruction. At commensurate electron density, the 3 p spectrum is shown to be almost unaffected by electronic correlations, however upon self-doping largely the normal and superconducting states. These findings provide a microscopic understanding of pressure-induced hole carrier superconductivity on the normal state coherence of s -wave superconductors with well-defined Bogoliubov quasiparticles at low temperatures. Upon internal thermalization, the s -wave superconducting state loses its phase coherence. [ABSTRACT FROM AUTHOR]

A novel Monte Carlo technique has been developed to determine lifetimes of excited states in the tens-to-hundreds femtoseconds range in products of low-energy heavy-ion binary reactions, with complex velocity distributions. The method is based on a detailed study of Doppler-broadened γ -ray lineshapes. Its relevance is demonstrated in connection with the 18 O (7.0 MeV/u) + 181 Ta experiment, performed at GANIL with the AGATA+VAMOS+PARIS setup, to study neutron-rich O, C, N,... nuclei. Excited states in 17 O and 19 O , with known lifetimes, are used to validate the method over the ∼ 20 - 400 fs lifetime-sensitivity range. Emphasis is given to the unprecedented position resolution provided by γ -tracking arrays, which turns out to be essential for reaching the required accuracy in Doppler-shift correction. The technique is anticipated to be an important tool for lifetime investigations in exotic neutron-rich nuclei, produced with intense ISOL-type beams. [ABSTRACT FROM AUTHOR]

Layered materials with buckled structure offer a promising route to explore distinct phases of quantum matter. Using GGA + DMFT we reveal the complex interplay between perpendicular electric field and site-diagonal disorder in the Dirac liquid electronic state of silicene. The electronic structure we derive is promising in the sense that it leads to results that might explain why out-of-plane electric field plus moderate disorder can generate marginal Dirac valleys consistent with scanning tunneling spectroscopy of silicene on Ag substrates. [ABSTRACT FROM AUTHOR]

We demonstrate the possibility to extract nuclear state femtosecond lifetimes from two-step γ ray cascades measured with a Ge-detector array. The technique is based on measuring the Doppler shift of a γ ray, caused by the recoil of a preceding γ ray emission. Since the two γ rays are populating/de-populating the same state they form a start/stop signal, the delay of which is compared to the slowing down motion of the nucleus within the target material. A multi-detector array combined with digital acquisition electronics in list mode, allows to measure several angular combinations and two-step cascades efficiently and simultaneously within one single experiment. The concept was demonstrated with the FIPPS array for the 35 Cl(n, γ) 36 Cl reaction, where we obtained good agreement with literature values showing the validity of the method. [ABSTRACT FROM AUTHOR]

The couplings between particles and vibrations in atomic nuclei play a key role in the understanding of various nuclear properties, as it has been highlighted along several decades. In this contribution, after a short survey of the early discoveries of particle-phonon multiplets around the 208Pb region, we review recent experiments and theoretical attempts to understand low-energy spectra of odd-nuclei close to magic and semi-magic cores, where particle-phonon coupling phenomena play a significant role. The focus will be on nuclei around 48Ca , 132Sn , 208Pb and neutron-rich Ni isotopes. Special emphasis will be given to experimental techniques based on high-resolution γ -spectroscopy and to recent theoretical developments aimed at disentangling particle-phonon coupled states and other more hybrid configurations, using the Hybrid Configuration Mixing model that has been recently proposed by the Milano group. [ABSTRACT FROM AUTHOR]

A combination of germanium detectors was installed at the PF1B neutron guide of the ILL to perform prompt spectroscopy of neutron-rich nuclei produced in the neutron-capture induced-fission of U and Pu. In addition, LaBr detectors from the FATIMA Collaboration were installed to complement with the EXOGAM clovers to measure lifetimes of low-lying excited states. The measured characteristics and online spectra indicate very good performances of the overall set-up. [ABSTRACT FROM AUTHOR]

Cross-sections of the main reaction channels for the collision Ne + Pb at 7.9MeV/u were studied using the radioactive ion beam delivered by the SPIRAL facility and the VAMOS-EXOGAM experimental set-up. Angular distributions for the elastic and inelastic channels were extracted, together with distributions for the +1 n and -1 p channels. A comprehensive description of the present data is made within the GRAZING model approach. [ABSTRACT FROM AUTHOR]

Excited states in the very neutron-deficient122La nucleus have been established for the first time using the92Mo(40Ca, 2α1 p1 n) reaction at beam energies of 190 and 200MeV. The observed transitions were grouped in three bands. Configurations have been assigned to the observed bands based on the properties extracted from the experimental data and on cranked shell model calculations. [ABSTRACT FROM AUTHOR]

The nuclear system at the limit of excitation energy and angular momentum is here studied in the case of the superdeformed nucleus 143Eu using &gama;-spectroscopy techniques. The data are based on a EUROBALL experiment using the reaction 37 Cl + 110Pd → 143Eu + 4n. The influence of thermal energy on sup erdeformed configurations is investigated through the analysis of the quasi-continuum spectra formed by E2 transitions among states of excited rotational bands with energy extending up to 4-5 MeV above the yrast line. In particular, the effective lifetimes of the discrete rotational bands forming ridge structures in γ-γ coincidence matrices is measured by a Doppler Shift Attenuation Method. The deduced quadrupole deformation of Qt ≈ 10 eb indicates that the nucleus maintains its collectivity with increasing excitation energy, supporting the superdeformed character of the excited nuclear rotation. The obtained number of sup erdeformed discrete bands forming the ridge structures is found in good agreement with microscopic cranked shell model calculations including the decay-out process into the lower deformation minimum. In addition, the nuclear properties at higher excitation energies are investigated through the E1 γ-decay of the giant dipole resonance (GDR). It is found that the intensity of the superdeformed yrast and excited bands increases by a factor of approximately 1.6 when a coincidence with a high-energy γ-ray is required, showing the importance of the E1 cooling in the feeding mechanism of the sup erdeformed states. [ABSTRACT FROM AUTHOR]

High-spin states of the nucleus 163Lu have been populated through the fusion-evaporation reaction 139La(29Si, 5n) with a beam energy of 157 MeV. In addition to the two lowest excited triaxial strongly deformed (TSD) bands, recently interpreted as one- and two-phonon wobbling excitations, a third excited TSD band has been firmly established decaying to the yrast TSD band. The assignment of this band as a three-quasiparticle band shows together with the normal deformed (ND) level scheme the presence not only of shape coexistence between ND and TSD structures, but also an interplay of wobbling and quasiparticle excitations in the triaxial strongly deformed potential well of 163Lu. [ABSTRACT FROM AUTHOR]

High-spin properties of the triaxial strongly deformed potential well in 163Lu at excitation energies above resolvable bands have been investigated. Gated Eγ- Eγ spectra display clear ridges with moments of inertia corresponding to those observed for the discrete strongly deformed bands. A fluctuation analysis of the ridges yields a number of two-step paths of ≈ 40 and ≈ 20, when gating on triaxial strongly or normally deformed bands, respectively. These results show that a potential well at large deformation coexists with the normally deformed well, and indicate a mixing between states in the two wells at higher excitation energy. [ABSTRACT FROM AUTHOR]

The rotational motion in thermally excited nuclei and its damping at high excitation energy is discussed here with reference to the role of effects beyond mean-field approximation. The experimental results for different mass regions and deformations are presented and compared with a cranked-shell-model calculation including a two-body residual interaction of surface delta type. Altogether, it is found that the dependence of the mixing process on the nuclear mass and deformation is well reproduced by the data. [ABSTRACT FROM AUTHOR]

The γ-decay of the Giant Dipole Resonance (GDR) built on excited nuclear states has been measured for the nucleus143Eu. The reaction110Pd(37Cl, 4 n)143Eu at a beam energy of 165 MeV has been employed. This experiment aimed at searching the γ-decay of the GDR built on the superdeformed143Eu states, populated at high spins. High-energy γ-rays were detected in 8 large BaF2 scintillators in coincidence with discrete transitions measured with the NORDBALL array (in the configuration consisting of 17 HPGe detectors and a 2π multiplicity filter). The spectrum of high-energy γ-rays gated by low-energy transitions between states fed by the superdeformed states shows some excess of yield in the 7–10 MeV region with respect to that gated by transitions between states not populated by the superdeformed states. This excess should be due to the γ-decay of the the giant dipole oscillation along the superdeformed axis of the nucleus that is expected to have a frequency corresponding to ≈9–10 MeV (low-energy component of the GDR strength function). The measured excess, in spite of the large error bars, is found to be of the same order as predicted statistical model values. [ABSTRACT FROM AUTHOR]

Theπh9/2[541 1/2−] band in 167Tm has been studied through the 124Sn(48Ca, p4n)167Tm reaction at Ebeam = 210 MeV. The favoured signature of the πh9/2[541 1/2−] band is observed to spin 61/2h̅. A remarkable small gain in aligned angular momentum at the AB-band crossing has been found. The crossing frequency and the gain in aligned angular momentum for 167Tm are compared with data for the N = 98 isotones of Lu, Ta and Re, and contrasted with Cranked Shell Model predictions, based on frequency diabatic configurations. Large deviations are found for the gain in aligned angular momentum. [ABSTRACT FROM AUTHOR]

The analysis of the fluctuations of the counts of unresolved γ-γ energy spectra can extend our knowledge of the rotational motion at high angular momentum and excitation energy above the yrast band. Detailed studies of the rotational quasi-continuum built on specific intrinsic nuclear configurations are here discussed. First, the validity of the K-selection rules in the quasi-continuum region is investigated in the case of the normal deformed nucleus Er. The γ cascades feeding into low-K and high-K bands are analyzed studying variance and covariance of the spectrum fluctuations. Low-K bands are found to be fed by a much larger effective number of cascades than high-K bands, while the covariance between pairs of gated spectra shows that the cascades feeding into low-K bands are different from those feeding into high-K bands. These findings suggest a persistence of K-selection rules in the region of excitation energy and angular momentum probed by the rotational decay of Er. As a second case, the existence of a rotational quasi-continuum in the super deformed well of Eu is discussed. An intense bump of rotationally correlated transitions is observed to develop as function of fold in the high spin region of gated spectra. Fold distribution, angular anisotropies, moment of inertia and life time show that the bump consists of fully damped super deformed transitions. This gives experimental evidence of damped rotational motion up to several MeV excitation energy above the super deformed yrast line. [ABSTRACT FROM AUTHOR]

We present shell model calculations for warm rotating nuclei, combining the cranked Nilsson mean field and a residual surface-delta two-body interaction. The model is used to describe the transition from the region of well-defined rotational bands into the region dominated by rotational damping, and the results are in overall agreement with the experimental findings. [ABSTRACT FROM AUTHOR]

Rotational motion loses its coherence as a function of the nuclear internal excitation energy. The damping process does not proceed in a continuous fashion and scars of discrete rotational bands are found, inbedded in a background of damped rotational states, regardless whether the calculations are carried out using effective or 'random' forces. The complexity of the damping mechanism is revealed in the lineshape of the ridges in the γ-γ correlation spectrum. [ABSTRACT FROM AUTHOR]

The strongly shape driving πh[541]l/2 configuration with α=+1/2 exhibits some anomalous, and so far unexplained, features concerning the crossing frequency, ħω, the aligned angular momentum, i, and interaction strength, at the alignment of the first pair of i quasineutrons in several odd-Z rare earth-nuclei. The h[541]1/2 and h[523]7/2 bands have been studied in the stably deformed rare-earth nucleusTm to investigate these features. A difference in band crossing frequency of ∼ 80 keV between the two bands is found. Rotational bands built on these two configurations have been found to cross in the spin range I=25/2-29/2 ħ. The γ-decay pattern between the two bands is established in the crossing region and analysed in terms of a moderate shape difference between them. A theoretical estimate of the size of the interaction strength between the two bands is presented and compared to the experimental value. The observed band structure inTm is very similar to that ofLu which has 2 protons and 2 neutrons in addition. This observation is discussed in relation to the similarity of the yrast bands of the two even-even 'core' nucleiEr andYb, for which the γ-transition energies are identical within ∼0.2 keV below the vi crossing. [ABSTRACT FROM AUTHOR]

The effect of cholesterol and fatty acid treatment in vitro was tested on rat liver plasma membrane-bound enzymes and lipid fluidity. The observed alterations of membrane fluidity affect both (Na−K)-ATPase and Mg-ATPase activities but not 5′-nucleotidase; basal adenylate cyclase as well as its hormonal sensitivity were differentially affected by changes of membrane microenvironment. [ABSTRACT FROM AUTHOR]

The number of discrete rotational bands in the nucleus 168Yb is obtained by a fluctuation analysis of the rotational ridge structure in double and triple γ coincidence matrices. The data are compared with cranked shell model calculations including a surface delta interaction. It is found that the number of calculated bands strongly depends on the interaction strength V0, and agreement between data and calculations supports the standard value V0= 27.5/A MeV. [ABSTRACT FROM AUTHOR]

The decay of 170W* formed in reactions with two different projectile - target combinations was studied. The observed differences in the average number of emitted neutrons suggest an entrance channel effect at the highest excitation energy and angular momentum. It may be explained by different excitation energies of the equilibrated system, resulting from the emission of pre-equilibrium α-particles during a longer fusion time, in the more symmetric reaction. [ABSTRACT FROM AUTHOR]

A rotational band with 15 transitions has been observed inEu in an experiment with the GASP Ge detector array by thePd(Cl,5) reaction. The average energy spacing between the neighbouring transitions is 60 keV, which is similar to the energy spacings in the superdeformed bands in the mass 140 region. The band has a constant dynamic moment of inertia as suggested by Cranked Shell Model calculations. [ABSTRACT FROM AUTHOR]

The γ-rays following the reaction 105 McV 18O | 28Si have been measured using the EUROBALL IV, HECTOR and EUCLIDES arrays in order to investigate the predicted Jacobi shape transition. The high-energy &gama;-ray spectrum from the GDR decay indicates the presence of large deformations in the hot 46Ti nucleus, in agreement with new theoretical calculations based on the rotating liquid-drop model. [ABSTRACT FROM AUTHOR]

During pregnancy the synthesis of cholesterol and the activity of 3-hydroxy 3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase fell markedly before parturition; HMGCoA synthase activity was low during pregnancy and fell again immediately before delivery while acetoacetyl-CoA-thiolase was always low and constant. [ABSTRACT FROM AUTHOR]

A search for the γ decay of the Giant Dipole Resonance built on superdeformed (SD) nuclear configurations of 143Eu was made, using the reaction 110Pd(37Cl, 4 n)143Eu at 165 MeV. Eight large BaF2 scintillators and the NORDBALL array were used to measure high and low-energy γ-rays. The γ-spectrum gated by transitions populated by the SD states shows an excess yield at 7-10 MeV compared to the spectrum gated by transitions not populated by SD states. The comparison with statistical model predictions indicates that this excess most probably is due to γ-ray emission of the GDR built on superdeformed states. [ABSTRACT FROM AUTHOR]

Several of the known rotational bands in 164Er are extended considerably (to around 35 h). In addition, a new coupled band is established and found to decay by an isomeric transition with t1/2 ≥ 170 nsec, to the 11t - state of the known Kπ =7− two-quasi-proton band. The new band is interpreted as a four-quasi-particle structure, with measured values of B(M1)/B(E2) consistent with the configuration [7t -] ⊗ ?i13/2[642 5/2+] ⊗ ?h9/2[523 5/2t -], i.e. [7t -]⊗ [AE,AF]. This is supported by the observation of a crossing which resembles the second i13/2 neutron crossing, BC, associated with the two-quasi-neutron band built on the configuration, [AE,AF]. The routhian of the new band is close to the sum of the individual routhians of [AE,AF] and [7−]. The cause of a small gain in energy of 130–272 keV is discussed. [ABSTRACT FROM AUTHOR]

Excited states inSn have been identified for the first time, in an in-beam γ-ray spectroscopic experiment. Two γ-ray transitions with energies 1472 and 497 keV following the decay of the seniority 6 isomer with t=1.0(5) μs were unambiguously assigned toSn. Due to the very low cross section of about 2 µb for producingSn in the reactionCr(Ni,1 α2n), a highly selective detector setup utilizing NORDBALL ancillary detectors and a recoil catcher device was used. High γ-ray detection efficiency was achieved with two EUROBALL Ge cluster detectors. [ABSTRACT FROM AUTHOR]

A discrete γ-ray transition with an energy of 3360.6 keV deexciting the second lowest SD state inEu has been discovered. It carries 3.2% of the full intensity of the band and feeds into a nearly spherical state which is above the I=35/2, E=4947 keV level. The exact placement of the single-step link is, however, not established due to the specially complicated level scheme in the region of interest. The energy of the single-step link agrees well with the previously determined two-step links. [ABSTRACT FROM AUTHOR]