Interacting Boson-fermion-fermion Model Research Articles

IBFFM Low-Lying States and Their Spin- Dependent Level Densities For Even-A Nuclei Associated with SU(6) Approximation and It’s O(6) Dynamical Symmetry of IBM

Objective: in this paper spin dependent level density dependence from dynamical, exchange particle-quasiparticle interactions and residual proton-neutron interactions are investigated. Theoretical framework: in the interacting boson-fermion-fermion model(IBFFM) for odd-odd nuclei 196Au the low-lying states and their densities are calculated for π d 3/2 , π d 5/2 , π s ½ , π h11/2 proton quasiparticles and ν p1/2, ν f5/2, ν p3/2, ν f7/2, ν i13/2 neutron quasiparticles and ν p1/2, ν f5/2, ν p3/2, ν f7/2, ν i13/2 neutron quasiparticles states, coupled to the IBM core in Su(6) approximation and it's O(6) dynamical symetry of interacting boson model (IBM). Method: we also applied cutting bosons and fermions space and investigated their impacts on spin dependent level density. The results are shown graphically and compared to the previous combinatorial, thermodynamic and spectral distribution approaches for 132Pr, 244 am and 114 Cd. Results and discussion: the IBFFM low-lying states up to 2 MeV are exactely in acordance with experimentala data. The IBFFM spin–dependent level densities can be well accounted by bethe and modified spin distribution formula. For small changes of dynamical, exchange and residual interactions we have a small changes in the spin-dependent level density of states. Research implications: the complex collective features and interplay between collective and quasiparticle degrees of freedom do not influence sizeable the IBFFM spin-dependent level density distribution. Originality/value: this study contributes to the literature of IBFFM low-lying states and their spin- dependent level densities for even-A nuclei.

An Application of Interacting Boson Fermion-Fermion Model (IBFFM) for <sup>134</sup>Cs Nucleus

This work concerns the calculations of interacting boson fermion-fermion model (IBFFM) for the odd-odd nucleus <sup>134</sup>Cs. The energy levels (positive and negative parity states), electric transition probability B(E2), magnetic transition probability B(M1), quadrupole and magnetic dipole moments have been studied in this work. The IBFFM results are compared with the available experimental data. In the present work, the IBFFM pattern of total and parametric dependent level densities for the odd-odd nucleus <sup>134</sup>Cs is investigated and compared to the pattern found in previous investigations in the framework of combinatorial and spectral distribution approaches. When comparing the theoretical values with the available experimental values, it was found that there is a good match between them. This is due to the values of the Hamiltonian parameters that were found accurately, so this IBFFM model is considered one of the effective models in studying the nuclear structure of odd-odd nuclei. The level density of the odd-odd nucleus <sup>196</sup>Au is investigated in the interacting boson-fermion-fermion model (IBFFM) which accounts for collectivity and complex interaction between quasiparticle and collective modes. The IBFFM spin-dependent level densities show high-spin reduction with respect to Bethe formula. This can be well accounted for by a modified spin-dependent level density formula.

New Interacting Boson Fermion-Fermion Model results

We present a new application of the Interacting Boson Model (IBM) and its extensions for describing double charge exchange reactions. The study of double charge exchange reactions induced by heavy ions involving candidate nuclei for neutrinoless double beta decay is a complex task carried out by the NUMEN collaboration. This investigation faces the intricacies of complex oddodd intermediate nuclei in sequential double charge exchange processes. We will offer a comprehensive description of heavy odd-odd nuclei using the Interacting Boson Fermion-Fermion Model (IBFFM). Additionally, we will outline the methodology for describing transfer operators within this framework. Finally, we will explore the potential applications of our results for describing double charge exchange reactions.

Transfer reactions between odd-odd and even-even nuclei by using the interacting boson fermion fermion model and 0νββ decay in closure approximation

Spectroscopic amplitudes (SAs) in the interacting boson fermion fermion model (IBFFM) are necessary for the computation of $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay but also for cross sections of heavy-ion reactions, in particular, double charge exchange reactions for the NUMEN Collaboration, if one does not want to use the closure limit. We present for the first time (i) the formalism and operators to compute in a general case the spectroscopic amplitudes in the IBFFM scheme from even-even to odd-odd nuclei, in a way suited to be used in reaction code, i.e., extracting the contribution of each orbital; (2) the odd-odd nuclei as described by the old IBFFM are obtained for the first time with the new implementation of machine learning (ML) techniques for fitting the parameters, getting a more realistic description. The one-body transition densities for $^{116}\mathrm{Cd}\ensuremath{\rightarrow}^{116}\mathrm{In}$ and $^{116}\mathrm{In}\ensuremath{\rightarrow}^{116}\mathrm{Sn}$ are part of the experimental program of the NUMEN experiment, which aims to find constraints on $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay matrix elements. As a first application of the spectroscopic amplitudes we present the calculation of the $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ nuclear matrix elements in the IBFFM formalism in closure approximation.

Two-neutrino double- β decay in the mapped interacting boson model

A calculation of two-neutrino double-$\beta$ ($2\nu\beta\beta$) decay matrix elements within the interacting boson model (IBM) that is based on the nuclear density functional theory is presented. The constrained self-consistent mean-field (SCMF) calculation using a universal energy density functional (EDF) and a pairing interaction provides potential energy surfaces with triaxial quadrupole degrees of freedom for even-even nuclei corresponding to the initial and final states of the $2\nu\beta\beta$ decays of interest. The SCMF energy surface is then mapped onto the bosonic one, and this procedure determines the IBM Hamiltonian for the even-even nuclei. The same SCMF calculation provides the essential ingredients of the interacting boson fermion-fermion model (IBFFM) for the intermediate odd-odd nuclei and the Gamow-Teller and Fermi transition operators. The EDF-based IBM and IBFFM provide a simultaneous description of excitation spectra and electromagnetic transition rates for each nucleus, and single-$\beta$ and $\beta\beta$ decay properties. The calculated $2\nu\beta\beta$-decay nuclear matrix elements are compared with experiment and with those from earlier theoretical calculations.

β decay of even- A nuclei within the interacting boson model with input based on nuclear density functional theory

We compute the $\beta$-decay $ft$-values within the frameworks of the energy density functional (EDF) and the interacting boson model (IBM). Based on the constrained mean-field calculation with the Gogny-D1M EDF, the IBM Hamiltonian for an even-even nucleus and essential ingredients of the interacting boson-fermion-fermion model (IBFFM) for describing the neighboring odd-odd nucleus are determined in a microscopic way. Only the boson-fermion and residual neutron-proton interaction strengths are determined empirically. The Gamow-Teller (GT) and Fermi (F) transition rates needed to compute the $\beta$-decay $ft$-values are obtained without any additional parameter or quenching of the $g_A$ factor. The observed $\ft$ values for the $\beta^+$ decays of the even-even Ba into odd-odd Cs nuclei, and of the odd-odd Cs to the even-even Xe nuclei, with mass $A\approx 130$ are reasonably well described. The predicted GT and F transition rates represent a sensitive test of the quality of the IBM and IBFFM wave functions.

Dynamic chirality in the interacting boson fermion-fermion model

The chiral interpretation of twin bands in odd-odd nuclei was investigated in the interacting boson fermion-fermion model. The analysis of the wave functions has shown that the possibility for angular momenta of the valence proton, neutron and core to find themselves in the favorable, almost orthogonal geometry is present, but not dominant. Such behavior is found to be similar in nuclei where both the level energies and the electromagnetic decay properties display the chiral pattern, as well as in those where only the level energies of the corresponding levels in the twin bands are close together. The difference in the structure of the two types of chiral candidates nuclei can be attributed to different \ensuremath{\beta} and \ensuremath{\gamma} fluctuations, induced by the exchange boson-fermion interaction of the interacting boson fermion-fermion model. In both cases the chirality is weak and dynamic.

STUDY OF β DECAY FROM EVEN-EVEN 124Ba TO ODD-ODD 124Cs IN THE INTERACTING BOSON-FERMION-FERMION MODEL

We study the β decay from an even-even nucleus 124 Ba to an odd-odd nucleus 124 Cs in the interacting boson-fermion-fermion model (IBFFM). The even-even nucleus is described by the proton-neutron interacting boson model (IBM2) while the odd-odd nucleus is by the proton-neutron interacting boson-fermion-fermion model (IBFFM2). The result shows that the model is applicable to β-decay as well as the energy levels and the electromagnetic properties.

Interacting boson fermion-fermion model calculation of theπh11∕2⊗νh11∕2doublet bands inPr134

The interacting boson fermion-fermion model is employed in the analysis of the positive-parity doublet bands in $^{134}\mathrm{Pr}$. It is shown that stable triaxial deformation gives rise to the experimentally observed crossing between the yrast and yrare bands built on the $\ensuremath{\pi}{h}_{11∕2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11∕2}$ configuration. The collective structure of the yrast band is basically built on the ground-state band of the triaxial core, whereas the collective structure of the yrare band is predominantly based on the $\ensuremath{\gamma}$ band of the core. The mixing between the two bands increases with angular momentum. A constant energy spacing between the two lowest positive-parity bands is predicted in other odd-odd $N=75$ nuclei with $\ensuremath{\gamma}$-soft potential energy surfaces.

Further evidence on shape coexistence in72As

The 72As nucleus was studied via the (α,nγ) reaction at 14.2 MeV bombarding energy. Single γ−,γγ-coincidence, and internal conversion electron spectra were measured with Ge(HP) γ-ray and superconducting magnetic lens plus Si(Li) electron spectrometers. On the basis of the internal conversion coefficients of72As transitions, parities of the medium-spin levels up to 1.4 MeV excitation energy were determined, resulting in unambiguous parities also for the heads of the bands observed previously. The states observed were assigned to proton-neutron multiplets on the basis of their decay properties. The energy splittings of the observed multiplets are in accordance with the prediction of the previous interacting boson-fermion-fermion model (IBFFM) calculations using a transitional core lying between the vibrational SU(5) and γ-soft O(6) limits, except that of the πg9/2νg9/2 multiplet, which was described using the deformed SU(3) core in the present IBFFM calculations. Such a core structure is in accordance with previous particle-rotor and Hartree-Fock-Bogoliubov calculations.

Structure of odd-odd Cu isotopes in the framework of the interacting boson-fermion-fermion model

In the present work, odd-odd ${}^{62,64,66}$Cu nuclei have been studied in the framework of the interacting boson-fermion-fermion model (IBFFM). Odd-odd Cu nuclei have been described with the parameters obtained from the IBM calculation for even Ni nuclei and the IBFM description of odd mass Cu and Ni nuclei. A simple delta interaction has been assumed between the odd neutron and the odd proton in the odd-odd nuclei. The calculated excitation energy values and the magnetic moments of odd Cu and Ni nuclei in the IBFM are compared to show the effectiveness of the parameters in explaining the low energy structure of these nuclei. Excitation energy spectra, magnetic moment and spectroscopic factors for the single-nucleon transfer reaction have been calculated for the odd-odd nuclei and are compared with the corresponding experimental values. The results seem to indicate the ability of the model to explain the low energy structure of odd-odd Cu nuclei.

Spin-dependent level density in interacting boson-fermion-fermion model

The level density of the odd-odd nucleus 132Pr is investigated in the interacting boson-fermion-fermion model (IBFFM) which accounts for collectivity and complex interaction between quasiparticle and collective modes. The IBFFM total level density is fitted by a Gaussian and its tail is also fitted by Bethe formula and constant temperature Fermi gas model. The IBFFM spin-dependent level densities show high-spin reductions with respect to Bethe formula. This can be well accounted for by a modified spin-dependent level density formula.

Beta + decay of 15.2-min 114Te.

The ${\mathrm{\ensuremath{\beta}}}^{+}$ decay of 15.2 min $^{114}\mathrm{Te}$ into levels of $^{114}\mathrm{Sb}$ was studied through \ensuremath{\gamma}-ray and conversion electron spectroscopy at the UNISOR on-line isotope mass separator. Multiscaled \ensuremath{\gamma}-ray and electron singles provided for the determination of energies and intensities for 94 transitions (68 new) and of internal conversion coefficients for 12 of these transitions. The level scheme was deduced from \ensuremath{\gamma}-\ensuremath{\gamma} and \ensuremath{\gamma}-e coincidence measurements and extended to 2.1 MeV. The energy spectrum and electromagnetic properties of levels and associated transitions were calculated in the interacting boson-fermion-fermion model (IBFFM), with good agreement between experimental and theoretical results. \textcopyright{} 1996 The American Physical Society.

Low-lying states in the doubly odd nucleus 132Pr from beta decay of 132Nd

Abstract The low-lying level scheme of the odd-odd nucleus 132Pr has been investigated for the first time. The radioactive nuclei were produced by bombarding 96Mo targets with a 225 MeV 40Ca beam. Levels in 132Pr have been populated from the 132Nd β-decay. A new value of its half-life has been measured: T 1 2 = 88 ± 7 s . The activities produced in the reaction have been transported with a He-jet device and γγt, Xγt, e−γt coincidence measurements performed. Internal conversion coefficients have been measured with a magnetic lens spectrometer. The experimental level scheme of 132Pr is compared to theoretical calculations performed with the interacting boson-fermion-fermion model (IBFFM).

Microscopic approach to the U(6/4 x 4)

Relations between the ${\mathrm{Spin}}^{\mathrm{BFF}}$(6) symmetry Hamiltonian for odd-odd systems and the interacting boson-fermion-fermion model (IBFFM) Hamiltonian are investigated. An exact equivalence is established by slightly revising the exchange term of the IBFFM Hamiltonian. The ${\mathrm{Spin}}^{\mathrm{BFF}}$(6) symmetry is realized approximately in IBFFM by extending the quasiparticle configuration space for odd fermions. The proton-neutron residual interaction associated with the appearance of dynamical symmetry is compared to effective proton-neutron forces.

Structure of 116Sb nucleus.

The \ensuremath{\gamma}-ray and internal conversion electron spectra of the $^{113}\mathrm{In}$(\ensuremath{\alpha},n\ensuremath{\gamma}${)}^{116}$Sb reaction have been measured at 14.5 and 16.0 MeV bombarding \ensuremath{\alpha}-particle energies with Ge(HP) \ensuremath{\gamma} and superconducting magnetic lens plus Si(Li) electron spectrometers. The energies and relative intensities of 189 $^{116}\mathrm{Sb}$ \ensuremath{\gamma} rays (including 117 new ones), as well as internal conversion coefficients of 59 $^{116}\mathrm{Sb}$ transitions, have been determined. \ensuremath{\gamma}\ensuremath{\gamma} coincidences have also been measured at ${\mathit{E}}_{\mathrm{\ensuremath{\alpha}}}$=16 MeV. Both low-spin and high-spin level schemes have been deduced and 32 new levels have been identified. Multipolarities of transitions and \ensuremath{\gamma}-ray branching ratios have been determined. The energy spectrum and electromagnetic properties have been calculated in the interacting-boson-fermion-fermion model (IBFFM), and satisfactory agreement between the experimental and theoretical results has been obtained.

Description of vibrational odd-odd nuclei with the interacting boson-fermion-fermion model

The vibrational symmetry limits of the interacting boson-fermion-fermion model (IBFFM) for odd-odd nuclei are studied when neutrons and protons occupy orbits with j = 1/2, 3/2 and 5/2. Three essentially different situations occur depending on whether the fermions are particles or holes. Applications are presented for the odd-odd nuclei 76As and 80Br.

Nuclear structure of 198Au studied with (n, γ) and (d, p) reactions and interpreted with the IBFFM

The 197Au(d, p) 198Au reaction was measured with the high-resolution Q3D spectrograph at the Munich Tandem Accelerator at θ lab = 35°, using 20 MeV deuterons. Average resonance neutron capture gamma rays were measured with a filtered neutron beam at the Brookhaven National Laboratory. Using also secondary (n, γ) data a level scheme of 198Au was established with 66 levels up to an excitation energy of 1600 keV mostly with spin and parity assignments. The level energies, E2 and M1 branching ratios and (d, p) transfer data were compared with new model predictions of the interacting boson-fermion-fermion model (IBFFM). This model provides a basic understanding of 198Au.

Proton-neutron multiplets in96Y

The structure of the nucleus 39 96 Y57 is discussed in the framework of the parabolic rule for the splitting of members of proton-neutron coupled configurations and of the interacting boson-fermion-fermion model (IBFFM). A good description of the available experimental data including the existence of theβ − decaying 8+ isomer with a half-life of 10 s has been obtained which demonstrates the influence of the subshell closures in the neighbourhood of 40 96 Zr56.

Low-lying states and degree of chaoticity of40K in IBFFM

The results of aγ-γ angular correlation and a low energyγ-ray singles measurement using thermal neutron capture in39K are presented. The properties of low-lying levels of40K are interpreted in a comparison of the experimental data with the Interacting-Boson-Fermion-Fermion Model (IBFFM). The level fluctuation properties of the IBFFM spectrum are analysed and a sizeable deviation from chaoticity is found.