Transition Strengths Research Articles

The societal strength of transition: a critical review of the circular economy through the lens of inclusion

ABSTRACT Realizing a circular economy (CE) has been widely recognized by practitioners and researchers as the key to the transition toward sustainability. Thus far the academic emphasis has been predominantly on economic and environmental aspects. However, the development and implementation of CE initiatives actually rely on extensive collaboration at the societal level. Hence, an understanding of how a more inclusive society can strengthen the transition is warranted. By systematically and critically reviewing the related academic literature, the results of this paper show that sensitivity to inclusion aspects is crucial to alleviate the transitional burdens on society. Seven main aspects were discerned on inclusion: (1) informal waste pickers, (2) e-waste and health risks, (3) accessibility of services/materials/facilities, (4) consumer behavior, (5) corporate and institutional involvement, (6) technology application, and (7) governance measures. Following these insights, a strong sustainability perspective and agenda on the CE transition are proposed by identifying key actors and structuring their interrelationships as an inclusive system.

Study of S, Cl and Ar isotopes with $$N \ge Z$$ using microscopic effective sd-shell interactions

In the present work, newly developed microscopic effective $sd$-valence shell interactions such as chiral next-to-next-to-next-to-leading order (N3LO), $J$-matrix inverse scattering potential (JISP16), Daejeon16 (DJ16), and monopole-modified DJ16 (DJ16A) are employed to study the nuclear structural properties of sulphur, chlorine, and argon isotopes with $N \geq Z$. These interactions are derived using the \textit{ab initio} no-core shell-model and the OLS unitary transformation method. We calculate energy spectra and electromagnetic properties to test the predictive strength of the effective interactions for these heavier $sd$-shell nuclei. For a complete systematic study, we compare the microscopic results with the phenomenological USDB results and experimental data. By looking at the excitation energies of these nuclei, the DJ16A interaction is found to be {the} most suitable for these $sd$-shell nuclei among all microscopic interactions. The electric quadrupole transition strength and excitation energy of the first $2^+$ state data of even-even sulphur isotopes indicate the presence of the $N=20$ shell closure. Quadrupole moment predictions are also made using these interactions where experimental data are unknown. Magnetic moments are in excellent agreement with the experimental values. The root-mean-square deviations are also calculated to provide an idea of how accurate the interactions are.

Axial and triaxial degrees of freedom in 72Zn

The unstable N=42 nucleus 72Zn has been studied using multiple safe Coulomb excitation in inverse kinematics. The experiment was performed at the REX-ISOLDE facility at CERN making first use of the silicon detector array C-REX in combination with the γ-ray spectrometer Miniball. The high angular coverage of C-REX allowed to determine the reduced transition strengths for the decay of the yrast 01+, 21+ and 41+ as well as of the 02+ and 22+ states in 72Zn. The quadrupole moments of the 21+, 41+ and 22+ states were extracted. Using model independent quadrupole invariants, the ground state of 72Zn was found to have an average deformation in the γ degree of freedom close to maximum triaxiality. In comparison to experimental data in zinc isotopes with N<40, the collectivity of the 41+ state in neutron-rich 72Zn is significantly larger, indicating a collective yrast band based on the ground state of 72Zn. In contrast, a low experimental B(E2;02+→21+) strength was determined, indicating a different structure for the 02+ state. Shell-model calculations propose a 02+ state featuring a larger fraction of the (spherical) N=40 closed-shell configuration in its wave function than for the 01+ ground state.The results were also compared with beyond mean field calculations which corroborate the large deformation in the γ degree of freedom, while pointing to a more deformed 02+ state. These experimental and theoretical findings establish the importance of the γ degree of freedom in the ground state of 72Zn, located between the 68,70Ni nuclei that have spherical ground states, and 76Ge, which has a rigid triaxial shape.

Effect of Nanoparticles and Their Anisometry on Adhesion and Strength in Hybrid Carbon-Fiber-Reinforced Epoxy Nanocomposites

Carbon-fiber-reinforced plastics are composite materials with record-high specific strength, which depends on the efficiency of stress redistribution between the reinforcing fibers by the polymer matrix. The problem is the accurate assessment of adhesion in the carbon fiber–polymer matrix system since it affects the overall strength of the composite. This paper provides a novel electrochemical method for determining adhesion by estimating the critical length of carbon fibers that protrude above the fracture surface of the fiber-reinforced composite using their electrical conductivity and insulating properties of the polymer matrix. The method has been successfully applied to evaluate adhesion in carbon plastics having an epoxy matrix filled with nanoparticles of different anisometry: carbon nanotubes, organomodified montmorillonite, or detonation nanodiamonds. In addition to adhesion measurements, the effect of nanoparticles on the viscosity of epoxy binder, its impregnation efficiency of carbon fibers, curing, glass transition, and tensile strength of fiber-reinforced composites was estimated. Nanodiamonds at a mass fraction of 0.1% proved to be the most effective for improving the quality of epoxy carbon plastics, increasing fiber–matrix adhesion by 2.5 times, tensile strength by 17%, and not decreasing the glass transition temperature.

The interfacial transition zone microstructure of ground ferronickel slag incorporated self-compacting concrete investigated by nanoindentation

The effect of using ground ferronickel slag (GFNS) as a supplementary binder on the interfacial transition zone (ITZ) and strength properties of self-compacting concrete (SCC) were investigated. Cement was replaced by 20–50% GFNS, and mechanical properties of the SCC were assessed. The ITZ was characterized by EDS line scanning. The elastic modulus and hardness properties of ITZ were determined by grid nanoindentation tests. Microstructural changes were followed up by XRD, SEM and EDS analysis, while the macro-level characterization was carried out by compressive and splitting tensile strengths. The strengths showed a decreasing trend with increasing GFNS content. The 28-day compressive strength of the mix with 35% GFNS was 66 MPa as compared to 79 MPa for the control mix. Moreover, up to 35% replacement level, this study finds a compatible ITZ, with a thickness of around 55 μm. The elastic modulus and the hardness values from the nanoindentation test suggest a decrease of the calcium silicate hydrate with the increase of GFNS that decreased strength. XRD data confirmed this finding. The line scanning data from EDS reveals that the presence of Al, Fe and S in ITZ was not significant. Hence, the Ca/Si ratio plays a pivotal role in determining the ITZ characteristic, which increases with the increase of GFNS content in the binder. Strength diminishes gradually with increasing Ca/Si ratio, possibly due to the damaged silicate skeleton and the hydrolytic weakening effect. Therefore, microstructural observations and nanoindentation results well elucidate the strength results, and these experimental outcomes will provide a strong base for utilizing GFNS in SCC.

Investigation of type-II Ga(As)Sb/GaAs quantum dots embedded in an InGaAs quantum well for solar cell applications

We theoretically investigate the electronic and optical properties of charge carriers in type-II Ga(As)Sb/GaAs quantum dots (QDs) embedded in an InGaAs quantum well (QW), to determine their viability for use in intermediate band solar cell (IBSC) devices. This hybrid structure has the advantage of allowing a large flexibility to alter wave function distribution of the electron ground state, which is often considered as an intermediate band (IB) in QD-IBSC. The polarized transitions dipole moment (TDM), the polarized absorption coefficients and the radiative lifetime were studied as a function of QD height. Our theoretical results show an enhancement of inter-band absorption spectrum with a redshift of the peak corresponding to h0→IB transition and a blueshift of the continuum→IB peak, as the height of QD increases. The intra-band light absorption spectrum exhibits a redshift and its magnitude remains almost unchanged, as the height of QD increases. Furthermore this structure provides strong intra-band light absorption comparable to that of type-I QDs and equivalent to h0→IB transition strength. A long carrier lifetime in IB of about 30ns was found, but remains more than an order of magnitude less than the inter-band radiative time due to the low confinement potentials of the electron along the ρ-axis in this type-II dot-in-well (DWELL) structure.

The interplay of single-particle and collective motions in the low-lying states of $$_\Lambda ^{21}$$ with quadrupole-octupole correlations

The beyond mean-field approach for low-lying hypernuclear states is extended by mixing the configurations associated with both single-particle and quadrupole-octupole collective excitations within the generator coordinate method based on a covariant density functional theory. The method is demonstrated in the application to the low-lying states of $$_\Lambda ^{21}$$ , where the configurations with the Λ hyperon occupying the first (Λs) and second (Λp) lowest-energy states are considered. The results indicate that the positive-parity states are dominated by the α + 12C + α + Λs structure. In contrast, the low-lying negative-parity states are dominated by a strong admixture of α +16O + Λs structure and α + 12C + α + Λp structure due to the inclusion of octupole correlations. As a result, the low-lying negative-parity states become much lower than what is expected from the previous studies without the mixing, and the electric multipole transition strengths are significantly quenched.

Magnetic quadrupole transitions in the relativistic energy density functional theory

Magnetic quadrupole (M2) excitation represents a fundamental feature in atomic nucleus associated to nuclear magnetism induced by spin and orbital transition operator. Since it has only been investigated within the non-relativistic theoretical approaches, and available experimental data are rather limited, it is interesting to study the properties of M2 transitions using the framework of relativistic nuclear energy density functional. In this work the nuclear ground state is calculated with relativistic Hartree-Bogoliubov model, while the M2 excitations are described using the relativistic quasiparticle random phase approximation with the residual interaction extended with the isovector-pseudovector term. The M2 transition strength distributions are described and analyzed for closed shell nuclei $$^{16}$$ O, $$^{48}$$ Ca, $$^{208}$$ Pb, open-shell $$^{18} \mathrm O$$ , $$^{42}$$ Ca, $$^{56}$$ Fe, and semi-magic $$^{90}$$ Zr. The evolution of M2 transition properties has been investigated within the $$^{36-64} \mathrm Ca$$ isotope chain. The main M2 transitions have rather rich underlying structure and detailed analysis shows that collectivity increases with the mass number due to larger number of contributing particle-hole configurations. Pairing correlations in open shell nuclei have strong effect, causing the reduction of M2 strength and shifts of the centroid energies to higher values. The analysis of M2 transition strengths indicate that considerable amount of experimental strength may be missing, mainly due to limitations to rather restricted energy ranges. The calculated M2 strengths for Ca isotopes, together with the future experimental data will allow constraining the quenching of the g factors in nuclear medium.

Electron-Impact Excitation and Dissociation of Heavy Rare Gas Heteronuclear Ions via Transitions to Charge Transfer States

Heteronuclear diatomic rare gas molecular cations feature excited electronic terms with charge transfer character located several eV above the ground term. The role of such terms in collisions involving heteronuclear ions is studied theoretically under conditions typical of the plasma-based sources of UV and IR radiation. Calculations were carried out for processes of dissociative excitation, dissociative recombination and electron impact bound–bound excitation in Ar/Xe and Kr/Xe plasmas using the recently developed semiclassical approach combined with the ab initio data for potential energy curves and oscillator strengths of electronic transitions. The approach consistently describes the contributions from the entire rovibrational manifold to the processes studied. The cross sections of the processes mentioned are calculated for wide ranges of gas temperatures and electron energies. We show that the processes considered are quite effective when they are accompanied by transitions to charge transfer terms. For the range of electron energies typical of active media of UV and IR radiation sources the cross sections exceed those reported for the processes usually considered to involve transitions between the ground and first excited electronic state. The excitation of charge transfer electronic terms can play an important role in the kinetics of rare gas mixture plasmas.

Oscillator strengths and cross sections of the valence-shell excitations of CH[formula omitted]I studied by fast electron scattering

Oscillator strengths and cross sections of the valence-shell excitations in CH3I are important for studying molecular photodissociation and monitoring the destruction of ozone in the Earth’s atmosphere. Based on the relative flow technique, absolute generalized oscillator strengths of the valence-shell excitations in CH3I have been determined by using an angle-resolved electron energy loss spectrometer. The measurement was carried out at an incident electron energy of 1.5 keV and an energy resolution of 80 meV. Optical oscillator strengths for the dipole-allowed transitions have been obtained at the zero limit of the squared momentum transfer, providing an independent cross check with the previous experimental results. The integral cross sections from the excitation threshold to 5000 eV have also been obtained by means of the BE-scaling method. The present experimental oscillator strengths and cross sections can supplement the fundamental spectroscopic data of CH3I and will play an important role in the studies of molecular photodissociation dynamics.

Simulations and analysis tools for charge-exchange (d, 2He) reactions in inverse kinematics with the AT-TPC

Charge-exchange (d,2He) reactions in inverse kinematics at intermediate energies are a very promising method to investigate the Gamow–Teller transition strength in unstable nuclei. A simulation and analysis software based on the attpcroot package was developed to study this type of reactions with the active-target time projection chamber (AT-TPC). The simulation routines provide a realistic detector response that can be used to understand and benchmark experimental data. Analysis tools and correction routines can be developed and tested from simulations in attpcroot, because they are processed in the same way as the real data. In particular, we study the feasibility of using coincidences with beam-like particles to unambiguously identify the (d,2He) reaction channel, and to develop a kinematic fitting routine for future applications. More technically, the impact of space-charge effects in the track reconstruction, and a possible correction method are investigated in detail. This analysis and simulation package constitutes an essential part of the software development for the fast-beams program with the AT-TPC.

Difluoroborate-based bichromophores: Symmetry relaxation and two-photon absorption

Given potential applications of multiphoton absorbers, in the present work we have studied the symmetry-relaxation effects in one- and two-photon absorption spectra in two bichromophore systems based on difluoroborate core linked by biphenylene or bianthracene moieties. We have employed a palette of experimental methods (synthesis, one- and two-photon spectroscopy, X-ray crystallography) and state-of-the-art computational methods to shed light on how symmetry relaxation, a result of twisting of building blocks, affects one- and two-photon absorption of the two studied fluorescent dyes. Electronic-structure calculations revealed that the planarity of central biphenyl moiety, as well as deviations from planarity up to 30–40 deg., ensure maximum values of two-photon transition strengths. Perpendicular arrangement of phenylene units in biphenylene moiety leads to 20% drop in the two-photon transition strengths. More detailed studies demonstrated that equilibrium structures of both compounds in chloroform solution show very different values of two-photon absorption cross sections at absorption band maxima, i.e. 224 GM for and 134 GM for biphenyle and bianthracene linkers, respectively. The latter value is in good agreement with experimental value obtained using Z-scan method. The difference in two-photon absorption cross section between both compounds can be rationalized based on equilibrium geometry differences, i.e. interplanar angle is 35 deg and 91 deg in the case of biphenylene and bianthracene moiety, respectively. It is thus not beneficial to introduce conformationally locked central linker based on bianthracene moiety.

Ab initio no-core shell-model study of 18-24Ne isotopes

We report ab initio no-core shell-model (NCSM) study of 18−24Ne isotopes for energy spectra, electromagnetic properties, and point-proton radii using three realistic NN interactions. We have used inside nonlocal outside Yukawa (INOY), charge-dependent Bonn 2000 (CDB2K) and the chiral next-to-next-to-next-to-leading order (N3LO) interactions. We are able to reach basis size up to N max = 6 for 18Ne and N max = 4 for the 19−24Ne isotopes with m-scheme dimensions up to 1.0 × 109 in case of 24Ne. We observed better results for INOY interaction in terms of the binding energies of the ground state, and overall all three interactions provide good agreement with the experimental low-energy spectra. Our results for reduced M1 transition strengths and magnetic moments are close to the experimental values. We found that for long-range observables such as the E2 transition strengths, the electric quadrupole moments, and the point-proton radii (r p ), we need higher N max calculations to obtain results comparable to the experimental data. We have observed almost 6% increment in the converged r p as we increase the model space from N max = 4 to N max = 6.

Dual electroweak phase transition in the two-Higgs-doublet model with the S3 discrete symmetry

In this work, dual electroweak phase transition (EWPT) consisting of two phases, is carefully studied in the two-Higgs-doublet model with the $S_3$ discrete symmetry. The role of $S_3$ here is to further separate the stages of the electroweak phase transition, compared to that of the original two-Higgs-doublet model (2HDM). The strength of the electroweak phase transition $(S)$ in the model under consideration is large enough for the first-order EWPT, specifically $1 < S < 2.8$. The ratio between the two vacuum expectation values (VEVs), $\tan\beta = v_2/v_1$, is proven to have no effects on the strength of the phase transition. This ratio only affects the mass domain that causes the first-order phase transition. Furthermore, in this paper we will show clearly that when studying the EWPT in models of more than one scalar field that generates masses, one needs to analyze the problem of phase transition under multiple stages. In other words, the effect of the first stage of symmetry breaking to the second one, is to simplify by suggestion that vacuum expectation value of the Higgs boson responsible for the initial stage is proportional to that of the field for the next stage.

Shape and multiple shape coexistence of nuclei within covariant density functional theory

Shape and multiple shape coexistence of nuclei are investigated throughout the nuclear chart by calculating the low-lying spectra and the quadrupole shape invariants for even-even nuclei with $10\leq Z\leq 104$ from the proton drip line to the neutron one within a five-dimensional collective Hamiltonian based on the covariant density functional PC-PK1. The quadrupole shape invariants are implemented to characterize the quadrupole deformations of low-lying $0^+$ states and predict nuclear mass regions of shape and multiple shape coexistence. The predicted low-lying spectra and the shape or multi-shape coexisting nuclei are overall in good agreement with the available experimental results. In addition, the present work predicts a wealth of nuclei with shape or multiple shape coexistence in the neutron-rich regions. The connection between the strong $E0$ transition strength and the occurrence of shape coexistence is analyzed systemically. It is found that nuclei with pronounced shape coexistence generally have strong $E0$ transition strengths, while the reverse may not be true. The present results can serve as useful guidelines for experimental searches and theoretical studies of shape and multiple shape coexistence, especially in neutron-rich regions.

High-resolution spectroscopy of a single nitrogen-vacancy defect at zero magnetic field

We report a study of high-resolution microwave spectroscopy of nitrogen-vacancy (NV) centers in diamond crystals at and around zero magnetic field. We observe characteristic splitting and transition imbalance of the hyperfine transitions, which originate from level anti-crossings (LACs) in the presence of a transverse effective field. We use pulsed electron spin resonance spectroscopy to measure the zero-field spectral features of single NV centers for clearly resolving such LACs. To quantitatively analyze the magnetic resonance behavior of the hyperfine spin transitions in the presence of the effective field, we present a theoretical model, which describes the transition strengths under the action of an arbitrarily polarized microwave magnetic field. Our results are of importance for the optimization of the experimental conditions for the polarization-selective microwave excitation of spin-1 systems in zero or weak magnetic fields.

Study of structure and radii for 20−31Na isotopes using microscopic interactions

In this work, Na isotopes with mass varying from A=20 to 31 have been studied using DJ16A, JISP16 and N3LO microscopic effective interactions in the sd-shell. These effective interactions are derived for sd-shell using no-core shell model wavefunctions and a unitary transformation method. We have also performed calculation with IMSRG effective interactions targeted for a particular nucleus. The studies include a detailed analysis of ground state binding energy, low-lying spectra, and electromagnetic properties such as reduced electric quadrupole transition strengths, quadrupole and magnetic dipole moments of the Na chain. The results obtained from these microscopic effective interactions were compared with the experimental data as well as with the results of phenomenological interaction USDB. The charge radii of Na isotopes are evaluated using shell model harmonic oscillator wave functions. In addition to charge radii, matter radii and neutron skin thickness in the Na chain are discussed with a focus on neutron-deficient Na isotopes.

Higgsless simulations of cosmological phase transitions and gravitational waves

First-order cosmological phase transitions in the early Universe source sound waves and, subsequently, a background of stochastic gravitational waves. Currently, predictions of these gravitational waves rely heavily on simulations of a Higgs field coupled to the plasma of the early Universe, the former providing the latent heat of the phase transition. Numerically, this is a rather demanding task since several length scales enter the dynamics. From smallest to largest, these are the thickness of the Higgs interface separating the different phases, the shell thickness of the sound waves, and the average bubble size. In this work, we present an approach to perform Higgsless simulations in three dimensions, producing fully nonlinear results, while at the same time removing the hierarchically smallest scale from the lattice. This significantly reduces the complexity of the problem and contributes to making our approach highly efficient. We provide spectra for the produced gravitational waves for various choices of wall velocity and strength of the phase transition, as well as introduce a fitting function for the spectral shape.

Level dynamics and avoided level crossings in driven disordered quantum dots

The statistical properties of the dynamics of energy levels are investigated in the case of two two-dimensional disordered quantum dot models with nearest neighbor hopping subjected to external time-dependent perturbations. While in the first model the external drivings are realized by a continuous variation of the on-site energies, in the second one it is generated by deformations of a parabolic potential. We concentrate on the effects of the potential on the localization properties and investigate the statistics of the energy level velocities and curvatures regarding their typical magnitudes and domain of agreement with the predictions of Random Matrix Theory (RMT) for the Gaussian Orthogonal, Unitary and Symplectic ensembles. Moreover, the statistical properties of the avoided level crossings are investigated in terms of the corresponding Landau-Zener parameters. We find that the strength of the Landau-Zener transitions exhibits universal behavior which also implies universal single-particle dynamics for slow perturbations independent of the disorder and potential strength, the system size and the symmetry class. These results can be verified experimentally by measurements of single-particle energy spectra in quantum dots.

Emergence of heavy quark spin symmetry breaking in heavy quarkonium decays

Heavy-quark spin symmetry (HQSS) implies that in the direct decay of a heavy quarkonium with spin $S$, only lower lying heavy quarkonia with the same spin $S$ can be produced. However, this selection rule, expected to work very well in the $b$-quark sector, can be overcome if multiquark intermediate states are involved in the decay chain, allowing for transitions to the final-state heavy quarkonia with a different spin ${S}^{\ensuremath{'}}$. In particular, the measured decays $\mathrm{\ensuremath{\Upsilon}}(10860)\ensuremath{\rightarrow}\ensuremath{\pi}{Z}_{b}^{(\ensuremath{'})}\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}\mathrm{\ensuremath{\Upsilon}}(nS)$ ($n=1$, 2, 3) and $\mathrm{\ensuremath{\Upsilon}}(10860)\ensuremath{\rightarrow}\ensuremath{\pi}{Z}_{b}^{(\ensuremath{'})}\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}{h}_{b}(mP)$ ($m=1$, 2) appear to have nearly equal strengths, which is conventionally explained by a simultaneous presence of both ${S}_{b\overline{b}}=0$ and ${S}_{b\overline{b}}=1$ components in the wave functions of the ${Z}_{b}\mathrm{s}$ in equal shares. Meanwhile, the destructive interference between the contributions of the ${Z}_{b}$ and ${Z}_{b}^{\ensuremath{'}}$ to the decay amplitude for a $\ensuremath{\pi}\ensuremath{\pi}{h}_{b}$ final state kills the signal to zero in the strict HQSS limit. In this paper, we discuss how the HQSS violation needs to be balanced by the narrowness of the ${Z}_{b}^{(\ensuremath{'})}$ states in the physical case to allow for equal transition strengths into final states with different total heavy quark spins, and how spin symmetry is restored as a result of a subtle interplay of the scales involved, when the mass of a heavy quark becomes infinite. Moreover, we demonstrate how similar branching fractions of the decays into $\ensuremath{\pi}\ensuremath{\pi}{h}_{b}$ and $\ensuremath{\pi}\ensuremath{\pi}\mathrm{\ensuremath{\Upsilon}}$ can be obtained and how the mentioned HQSS breaking can be reconciled with the dispersive approach to the $\ensuremath{\pi}\ensuremath{\pi}/K\overline{K}$ interaction in the final state and matched with the low-energy chiral dynamics in both final states.