Ground-state Band Research Articles

Rotational properties and blocking effects in N = 152 isotones 254No, 255Lr, and 256Rf

Abstract The ground-state bands in the N = 152 isotones 254No, 255Lr, and 256Rf are investigated by using the cranked shell model (CSM) with pairing correlations treated by the particle-number-conserving (PNC) method. The experimentally kinematic moments of inertia are all reproduced quite well by the PNC-CSM calculations, and the contributions to J(1) from neutrons exhibit remarkable similarities. Compared to 254No, the observed identity of J(1) in 256Rf is due to the negligible contribution to J(1) from the two more protons partially occupying the π[514]7/2, π[521]1/2, and π[624]9/2 orbitals. The increase of J(1) observed in the odd-A nucleus 255Lr, compared to those of the neighboring even-even isotones 254No and 256Rf, is attributed to the contribution of proton j(1)([521]1/2) due to the blocking of nucleon on the proton π[521]1/2 orbital. Compared to the case in heavier isotones 255Lr and 256Rf, the different behavior of B(E2) value above hω ∼ 0.20 MeV in 254No is predicted due to the level π[514]7/2 crossing with π[521]1/2.

An Investigation into Properties for (_66^156)Dy Isotope Using IBM-1 and IVBM Model

Abstract: The (_66^156)Dy isotopes in the O (6) region were investigated. The positive ground-state band of (_66^156)Dy nuclei was calculated using the interacting boson model ‎(IBM-1) and the interacting vector boson model (IVBM). The negative parity band energies of the above isotope were calculated using (IVBM) only. We plotted the ratios ((E(I+2))/(〖E(2〗_1^+)), (E(I+2))/(E(I)),r(((I+2))/I)) and the E-GOS curve as a function of the spin (I) to investigate the properties of the yrast band. Accordingly, the best-fit values of the parameters were used to construct the Hamiltonian, and the electromagnetic transition probability B(E2) of this nucleus was determined. Theoretical energy levels of dysprosium-156 isotope with a neutron number N = 90 and spin parity up to 〖30〗_1^+ were obtained using the MATLAB-20 simulation program. A comparison of these calculated energy levels with the corresponding experimentally measured ones shows a good agreement. The results also ‎draw our attention to the fact that the nucleus of interest deforms and exhibits gamma-instability ‎properties. Keywords: Dysprosium Isotopes, Even-even nuclei, Interacting Boson Model-1, Interacting Vector Boson Model, Negative parity, Yrast band. Abbreviations and Acronyms, IBM: Interacting Boson Model, IVBM: Interacting Vector Boson Model, U(5): Spherical limit, SU(3): Axially deformed shape limit O(6): γ-unstable limit, SP(12; R): the non-compact symplectic group.

Broadband terahertz absorption and Q-switching behavior of 5-chloro-2-nitroaniline (5C2NA) crystals

Abstract Growth of transparent 5-chloro-2-nitroaniline (5C2NA) crystals was achieved through the slow evaporation technique. Analysis via X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy confirmed the crystalline nature of the organic crystals and revealing distinct molecular fingerprints of 5C2NA respectively. UV-VIS and Photoluminescence (PL) spectroscopy were employed to study the material's band gap and ground state absorption respectively. Thermogravimetric analysis (TGA) analysis indicated the stability of the grown crystals up to 211ºC. Dielectric measurements and Urbach plot suggested the presence of fewer defects in 5C2NA crystals. Time domain terahertz spectroscopy was utilized to observe the variation of absorption coefficient and refractive index in the terahertz frequency regime. Nonlinear optical effects such as saturable absorption (SA) and reverse saturable absorption (RSA), are pivotal in the development of all-optical logic gates. The transition between SA and RSA possesses a significant importance in optoelectronic applications. In this study, we investigate the 5C2NA crystal, revealing its ability to exhibit both SA and RSA under Z scan technique with varying pump intensities. The switching properties observed in 5C2NA can be harnessed for applications such as all-optical logic gates, rapid optical switching, optical limiting, mode storage, and more.

First-Principles Computational Screening of Two-Dimensional Polar Materials for Photocatalytic Water Splitting.

The band gap constraint of the photocatalyst for overall water splitting limits the utilization of solar energy. A strategy to broaden the range of light absorption is employing a two-dimensional (2D) polar material as photocatalyst, benefiting from the deflection of the energy level due to their intrinsic internal electric field. Here, by using first-principles computational screening, we search for 2D polar semiconductors for photocatalytic water splitting from both ground- and excited-state perspectives. Applying a unique electronic structure model of polar materials, there are 13 photocatalyst candidates for the hydrogen evolution reaction (HER) and 8 candidates for the oxygen evolution reaction (OER) without barrier energies from the perspective of the ground-state free energy variation calculation. In particular, Cu2As4Cl2S3 and Cu2As4Br2S3 can catalyze HER and OER simultaneously, becoming promising photocatalysts for overall water splitting. Furthermore, by combining ground-state band structure calculations with excited-state charge distribution and transfer calculated by linear-response time-dependent density functional theory (LR-TDDFT) and time-dependent ab initio nonadiabatic molecular dynamics (NAMD), respectively, the rationality of the 2D polar material model has been manifested. The intrinsic built-in electric field promotes the separation of charge carriers while suppressing their recombination. Therefore, our computational work provides a high-throughput method to design high-performance photocatalysts for water splitting.

Ultrafast planarization of photoexcited ligands in metal–organic frameworks gates charge transfer to promote photocatalysis

Metal–organic frameworks (MOFs) have emerged as a highly tunable class of porous materials with wide-ranging applications from gas capture to photocatalysis. Developing these exciting properties to their fullest extent requires a thorough mechanistic understanding of the structure–function relationships. We implement an ultrafast spectroscopic toolset, femtosecond transient absorption and femtosecond stimulated Raman spectroscopy (FSRS), to elucidate the correlated electronic and vibrational dynamics of two isostructural 1,3,6,8-tetrakis(p-benzoic acid)pyrene (TBAPy)-based MOFs, which manifest drastically different photocatalytic behaviors. Systematic comparisons between the M3+-TBAPy MOFs and bare ligands in various environments reveal the unproductive dimer formation in Al-TBAPy, whereas Sc-TBAPy is dominated by a catalytically active charge-transfer (CT) process. Two ground-state FSRS marker bands of the TBAPy ligand at ∼1267 and 1617 cm−1 probe the chromophore environment at thermal equilibrium. For comparison, the excited-state FSRS of Sc-TBAPy suspended in neutral water unveils a key ∼300 fs twisting motion of the TBAPy peripheral phenyl groups toward planarity, promoting an efficient generation of CT species. This motion also exhibits high sensitivity to solvent environment, which can be a useful probe; we also showed the CT variation for ultrafast dynamics of Sc-TBAPy in the glyphosate aqueous solution. These new insights showcase the power of table-top tunable FSRS methodology to delineate structural dynamics of functional molecular systems in action, including MOFs and other photosensitive “nanomachines.” We expect the uncovered ligand motions (ultrafast planarization) to enable the targeted design of new MOFs with improved CT state characteristics (formation and lifetime) to power applications, including photocatalysis and herbicide removal from waterways.

Effective Manipulation of a Colossal Second-Order Transverse Response in an Electric-Field-Tunable Graphene Moiré System.

The second-order nonlinear transport illuminates a frequency-doubling response emerging in quantum materials with a broken inversion symmetry. The two principal driving mechanisms, the Berry curvature dipole and the skew scattering, reflect various information including ground-state symmetries, band dispersions, and topology of electronic wave functions. However, effective manipulation of them in a single system has been lacking, hindering the pursuit of strong responses. Here, we report on the effective manipulation of the two mechanisms in a single graphene moiré superlattice, AB-BA stacked twisted double bilayer graphene. Most saliently, by virtue of the high tunability of moiré band structures and scattering rates, a record-high second-order transverse conductivity ∼ 510 μm S V-1 is observed, which is orders of magnitude higher than any reported values in the literature. Our findings establish the potential of electrically tunable graphene moiré systems for nonlinear transport manipulations and applications.

Hot carrier dynamics in metalated porphyrin-naphthalimide thin films.

This study employs femtosecond transient absorption spectroscopy to investigate the rapid dynamics of excited state carriers in three metalated porphyrin-naphthalimide (PN) molecules and one free-base molecule. The dynamics of electron injection, from PN to mesoporous titania (TiO2), in PN adsorbed TiO2 films (Ti-PN), were carefully investigated and compared to PN adsorbed ZrO2 films (Zr-PN). In addition, we examined the self-assembled PN films and found that, in their self-assembled state, these molecules exhibited a longer relaxation time than Zr-PN monomeric films, where the charge injection channel was insignificant. The ground-state bleach band in the Ti-PN films gradually shifted to longer wavelengths, indicating the occurrence of the Stark effect. Faster electron injection was observed for the metalated PN systems and the electron injection times from the various excited states to the conduction band of TiO2 (CB-TiO2) were obtained from the target model analysis of the transient absorption spectra data matrix. In these metal-organic complexes, hot electron injection from PN to CB-TiO2 occurred on a time scale of <360 fs. Importantly, Cu(II)-based PN complexes exhibited faster injection and longer recombination times. The injection times have been estimated to result from a locally excited state at ≈280 fs, a hot singlet excited state at 4.95 ps, and a vibrationally relaxed singlet excited state at 97.88 ps. The critical photophysical and charge injection processes seen here provide the potential for exploring the underlying factors involved and how they correlate with photocatalytic performance.

β and γ vibrations in the IBM

The properties of β- and γ-bands are analyzed in the framework of the IBM. It is shown that the general features of the observed excitation energies and the transition probabilities to the ground state band can be explained simply in terms of the intrinsic states of the IBM.

Transitional character of Nd-Dy (N=90) isotones in IBM model

The Interacting Boson Model is used to study the level structure of ground state, beta, and gamma bands in150Nd, 152Sm, 154Gd and 156Dy (N = 90) isotones. The energy ratios R_((I+2)⁄2) and R_(0_2⁄2_1 ) are compared to the predictions of U(5), SU(3), and X(5) symmetry. The calculated reduced transition probabilities as well as quadrupoles moments were compared to experimental data. IBM-1 investigates the properties of the potential energy surface to determine the nuclear shape of the Nd-Dy (N=90) isotones.

Octupole correlations in the N = Z + 2 = 56 110Xe nucleus

This letter reports on the first observation of an octupole band in the neutron-deficient (N=Z+2) nucleus 110Xe. The 110Xe nuclei were produced via the 54Fe(58Ni,2n) fusion-evaporation reaction. The emitted γ rays were detected using the jurogam 3γ-ray spectrometer, while the fusion-evaporation residues were separated with the MARA separator at the Accelerator Laboratory of the University of Jyväskylä, Finland. The experimental observation of the low-lying 3− and 5− states and inter-band E1 transitions between the ground-state band and the octupole band proves the importance of octupole correlations in this region. These new experimental data combined with theoretical calculations using the symmetry-conserving configuration-mixing method, based on a Gogny energy density functional, have been interpreted as an evidence of enhanced octupole correlations in neutron-deficient xenon isotopes.

Nuclear Structure and Decay Data for A = 222 Isobars

Evaluated data are presented for 11 known A=222 nuclides (Bi, Po, At, Rn, Fr, Ra, Ac, Th, Pa, U, and Np), and relevant Jπ and T1/2 data for A=226 nuclei decaying by α-decay to A=222 nuclei. For 222Bi, only the isotopic identification is established with no measurement of its half-life. For 222Po, 222At, 222Fr, 222U, and 222Np, data are available only for the ground states, with static magnetic dipole and electric quadrupole moments, and charge radius measurements for the 222Fr ground state. For 222Ac and 222Pa, two low-lying levels are known from 226Pa α decay, and 226Np decay, respectively, but with no information about Jπ assignments and γ decays of these levels. For 222Pa, a long-lived isomeric state is known, decaying dominantly by α decay. 222Rn, 222Ra, and 222Th have been investigated in detail, the low-spin states by α decay and the high-spin studies of ground-state and octupole bands by in-beam γ-ray studies for all the three nuclei, as well as by Coulomb excitation for 222Rn and 222Ra. Low-spin levels in 222Ra have been investigated also through the β− decay of 222Fr. Half-lives of the excited states are known for 7 levels in 222Rn, 12 levels in 222Ra, and 3 levels in 222Th. Octupole deformations, with the presence of alternating-parity bands up to (16+) and (21−) in 222Rn, (20+) and (19−) in 222Ra, and (26+) and (25−) in 222Th, and with interband E1 transitions, have been established in these three nuclei. The present evaluation supersedes the previous A=222 ENSDF evaluations: (2011Si24), (1996El01), (1987El06) and (1977To14).

An improved microscopic core–quasiparticle coupling model for spectroscopy of odd-mass nuclei with octupole correlations

The microscopic core–quasiparticle coupling model for odd-A nuclei with octupole correlations is extended to include the monopole, quadrupole and octupole couplings between the core and the odd nucleon, based on the framework of covariant density functional theory. The model is tested in a study of low-lying excitation spectra for the odd-A nucleus [Formula: see text]Ra. Theoretical results, e.g., the parity doublets, interband [Formula: see text] and intraband [Formula: see text], are in very good agreement with the available data. In particular, the description of signature splitting in the ground-state band has been improved. This method provides a very useful tool for a systematic study of low-energy spectra in odd-mass actinides with octupole correlations.

Signatures for shape coexistence and shape/phase transitions in even–even nuclei

Systematics of B(E2) transition rates connecting the first excited state to the first excited state of the ground state band in even–even nuclei indicates that shape coexistence of the ground state band and the first excited K = 0 band should be expected in nuclei lying within the stripes of nucleon numbers 7–8, 17–20, 34–40, 59–70, 96–112 predicted by the dual shell mechanism of the proxy-SU(3) model, avoiding their junctions, within which high deformation is expected. Systematics of the excitation energies of the states in even–even nuclei show that shape coexistence due to proton-induced neutron particle-hole excitations is related to a first-order shape/phase transition from spherical to deformed shapes, while shape coexistence due to neutron-induced proton particle-hole excitations is observed along major proton shell closures.

Investigation of nuclear structure for [formula omitted] isotope using interacting boson model

The interacting boson model (IBM-1) is appropriate for describing nuclear levels of positive parity of even–even nuclei only. IBM-1 was used to calculate energy ratios, energy levels, and energy transitions for Xe8854142 isotope that belongs to mixed dynamical symmetry O(6)-U(5). Through IBM-1 we find that the number of energy levels decreases with decreases in the bosons number, for Xe8854142 isotope (N ​= ​5), so the energy levels did not exceed (L ​= ​10). The energy levels were calculated for Xe8854142 isotope, and most of their values were in good agreement with the experimental data, the spin, and the parity of some of the energy levels of the ground state band (which were unconfirmed experimentally) was confirmed and represented by (41+,61+,81+,101+) levels. Some energy levels were predicted, represented by (02+,22+,42+,62+) levels, in addition to predicting energy transitions for many other levels.

Gamma spectroscopy of even-even Ytterbium isotopes

The even-even Ytterbium isotopes lack spectroscopic information with the increase of the neutron number and they are well deformed nuclei, presenting rotational properties. In this mass region of the nuclear chart predictions have shown rare phenomena related to nuclear structure, such as shape coexistence. In this work the population of excited states were investigated in the even-even Yb isotopes via the 2n-transfer reaction 168-174Yb (18O, 16O) 170-176Yb. The measurements were carried out at the 9 MV Tandem accelerator at the Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH) in Romania. The deduced gamma-ray angular distributions in the ground state bands are found to correspond with transitions, as expected

Extending the metal to insulator transitions of rare‐earth nickelates towards low temperature ranges

AbstractAlthough the d‐band correlated rare‐earth nickelates (ReNiO3) exhibit broadly adjustable metal to insulator transitions (MIT) that enables emerging correlated electronic applications, it is yet difficult to regulate their associated critical temperature (TMIT) below 100 K. Herein, we extend the lower limit in TMIT of ReNiO3 down to 83 K while maintaining an abrupt switch in resistivity via partial La‐substitution of PrNiO3. The near edge X‐ray fine structure analysis and density function theory calculations indicate the strengthening in the metallic orbital configuration and reduction in the ground state band gap via La‐substitution of Re in NdNiO3 and PrNiO3. In contrast, analogous Ce substitution cannot reduce the TMIT of ReNiO3 owing to its valance variability toward +4, while La partial substitution of ReNiO3 with middle or heavy rare‐earth (e.g., Sm) easily disturb the co‐occupation of the Re‐site by the two rare‐earths as one dispersive phase.

α+Zr92 cluster structure in Mo96

In the evaluation of the half-life of the neutrinoless double-$\ensuremath{\beta}$ decay ($0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$) of a doubly closed-subshell nucleus $^{96}\mathrm{Zr}$, the structure of the nucleus $^{96}\mathrm{Mo}$ is essentially important. The $\ensuremath{\alpha}$-clustering aspects of $^{96}\mathrm{Mo}$ are investigated for the first time. By studying the nuclear rainbows in $\ensuremath{\alpha}$ scattering from $^{92}\mathrm{Zr}$ at high energies and the characteristic structure of the excitation functions at the extreme backward angle at the low-energy region, the interaction potential between the $\ensuremath{\alpha}$ particle and the $^{92}\mathrm{Zr}$ nucleus is determined well in the double folding model. The validity of the double folding model was reinforced by studying $\ensuremath{\alpha}$ scattering from neighboring nuclei $^{90}\mathrm{Zr}, ^{91}\mathrm{Zr}$, and $^{94}\mathrm{Zr}$. The double-folding-model calculations reproduced well all the observed angular distributions over a wide range of incident energies and the characteristic excitation functions. By using the obtained potential the $\ensuremath{\alpha}+^{92}\mathrm{Zr}$ cluster structure of $^{96}\mathrm{Mo}$ is investigated in the spirit of a unified description of scattering and structure. The existence of the second-higher nodal band states with the $\ensuremath{\alpha}+^{92}\mathrm{Zr}$ cluster structure, in which two more nodes are excited in the relative motion compared with the ground band, is demonstrated. The calculation reproduces well the ground-band states of $^{96}\mathrm{Mo}$ in agreement with experiment. The experimental $B(E2)$ value of the transition in the ground band is also reproduced well. The effect of $\ensuremath{\alpha}$ clustering in $^{96}\mathrm{Mo}$ on the the half-life of the $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ double-$\ensuremath{\beta}$ decay of $^{96}\mathrm{Zr}$ is discussed.

Conjectured Hole States (7Be, 19F) and p-h states (8Be) of the CSM

The remarkable success of the Algebraic Cluster Model (ACM) to describe the N=Z even-even light nuclei, 8Be, 12C, 16O and 20Ne, and the neighbouring nuclei with one particle added, 9Be, 9B, 13C, 21Ne and 21Na, using the Cluster Shell Model (CSM), lead us to consider the phenomenology of data on conjectured hole states of the CSM in 7Be and 19F, and conjectured high lying particle-hole states (p-h) in 8Be.We propose the first application of the Cluster Shell Model (CSM) of Della Rocca and Iachello to conjectured p-h states in 8Be. We demonstrate a few essential phenomenological features of the CSM in 8Be: 1) All predicted conjectured p-h states of the CSM, and only the predicted p-h states, are observed near thresholds and up to 19.5 MeV in 8Be. 2) The states are observed in the predicted order, with positive parity states below negative parity states. 3) Some of the conjectured p-h states are already known to have the predicted rotational structure of the deformed p-h states. 4) The rotational structures observed at high excitations in the conjectured p-h bands in 8Be, resemble the ground state bands of 8Be, 9Be and 9B, with similar moment of inertia.Based on these observations we contemplate new measurements of the spectroscopy of 8Be at energies above 19.5 MeV, where our knowledge of states in 8Be is incomplete. We examine the observed B(M1)s and B(E2)s in these nuclei and contemplate a measurement of the B(E2) of the iso-baric Analog transition in 8Li.

Spectroscopic quadrupole moments in Xe124

Background: The Xe isotopic chain with four valence protons above the Z=50 shell closure is an ideal laboratory for the study of the evolution of nuclear deformation. At the N=82 shell closure, Xe136 presents all characteristics of a doubly closed shell nucleus with a spherical shape. In the very neutron-deficient isotopes close to N=50, the α-decay chain of Xe was investigated to probe the radioactive decay properties near the drip-line and the magicity of Sn100. Additionally, the Xe isotopes present higher order symmetries in the nuclear deformation such as the octupole degree of freedom near N=60 and N=90 or O(6) symmetry in stable isotopes. Purpose: The relevance of the O(6) symmetry has been investigated by measuring the spectroscopic quadrupole moment of the first excited states in Xe124. In the O(6) symmetry limit, the spectroscopic quadrupole moment of collective states is expected to be null. Method: A stable Xe124 beam with energies of 4.03A MeV and 4.11A MeV was used to bombard a natW target at the GANIL facility. Excited states were populated via the safe Coulomb excitation reaction. The collision of the heavy ions with a large Z at low energy make this reaction sensitive to the diagonal E2 matrix element of the excited states. The recoils were detected in the VAMOS++ magnetic spectrometer and the γ rays in the AGATA tracking array. The least squares fitting code gosia was used for the analysis to extract both E2 and M1 transitional and E2 diagonal matrix elements. Results: The rotational ground state band was populated up to the 81+ state as well as the 22+ and 42+ states. Using high precision spectroscopic data to constrain the gosia fit, the spectroscopic quadrupole moments of the 21+, 41+, and 61+ states were determined for the first time. Conclusions: The spectroscopic quadrupole moments were found to be negative, large, and constant in the ground state band underlining the prolate axially deformed ground state band of Xe124. The present experimental data confirm that the O(6) symmetry is substantially broken in Xe124.1 MoreReceived 21 October 2022Accepted 23 January 2023DOI:https://doi.org/10.1103/PhysRevC.107.014324©2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCollective levelsElectromagnetic transitionsSpectroscopic factors & electromagnetic momentsProperties90 ≤ A ≤ 149Nuclear Physics

Islands of Shape Coexistence: Theoretical Predictions and Experimental Evidence

Parameter-free theoretical predictions based on a dual shell mechanism within the proxy-SU(3) symmetry of atomic nuclei, as well as covariant density functional theory calculations using the DDME2 functional indicate that shape coexistence (SC) based on the particle-hole excitation mechanism cannot occur everywhere on the nuclear chart but is restricted on islands lying within regions of 7–8, 17–20, 34–40, 59–70, 96–112, 146–168 protons or neutrons. Systematics of data for even-even nuclei possessing K=0 (beta) and K=2 (gamma) bands support the existence of these islands, on which shape coexistence appears whenever the K=0 bandhead 02+ and the first excited state of the ground state band 21+ lie close in energy, with nuclei characterized by 02+ lying below the 21+ found in the center of these islands. In addition, a simple theoretical mechanism leading to multiple-shape coexistence is briefly discussed.