Search results for "SHELL model"
showing 10 items of 146 documents
No-core configuration-interaction model for the isospin- and angular-momentum-projected states
2016
[Background] Single-reference density functional theory is very successful in reproducing bulk nuclear properties like binding energies, radii, or quadrupole moments throughout the entire periodic table. Its extension to the multi-reference level allows for restoring symmetries and, in turn, for calculating transition rates. [Purpose] We propose a new no-core-configuration-interaction (NCCI) model treating properly isospin and rotational symmetries. The model is applicable to any nucleus irrespective of its mass and neutron- and proton-number parity. It properly includes polarization effects caused by an interplay between the long- and short-range forces acting in the atomic nucleus. [Metho…
New isomers in the full seniority scheme of neutron-rich lead isotopes: The role of effective three-body forces
2012
The neutron-rich lead isotopes, up to Pb216, have been studied for the first time, exploiting the fragmentation of a primary uranium beam at the FRS-RISING setup at GSI. The observed isomeric states exhibit electromagnetic transition strengths which deviate from state-of-the-art shell-model calculations. It is shown that their complete description demands the introduction of effective three-body interactions and two-body transition operators in the conventional neutron valence space beyond Pb208. © 2012 American Physical Society.
Geant4-aided Quantum State Selective Decay Spectroscopy of 213 Ra
2017
Utilizing the excellent mass resolving power of SHIPTRAP and the charged-particle-g multicoincidence setup TASISpec, the decay path of the 213Ra ground state can be exclusively studied. Based on virtual experiments with Geant4 it is possible to refine the a-branching ratios of the 213Ra ground state as well as g-ray branching ratios in the 209Rn daughter. The present study provides a proof of concept where clean quantum-state selective particle-g decay spectroscopy is used in conjunction with detailed Geant4 Monte-Carlo simulations to gain insight into nuclear structure properties.
Calculations of the atomic structure of the KNbO3 (110) surface
2000
Abstract The O-terminated KNbO 3 (110) surface is modeled using a semi-empirical shell model and two different short-range interatomic potentials. We find this surface to be unstable with respect to a strong reconstruction and K-termination. This conclusion is confirmed by preliminary calculations using the ab initio linear combination of atomic orbitals (LCAO) formalism.
Neutral-Current Neutrino-Nucleus Scattering off Xe Isotopes
2018
Large liquid xenon detectors aiming for dark matter direct detection will soon become viable tools also for investigating neutrino physics. Information on the effects of nuclear structure in neutrino-nucleus scattering can be important in distinguishing neutrino backgrounds in such detectors. We perform calculations for differential and total cross sections of neutral-current neutrino scattering off the most abundant xenon isotopes. The nuclear structure calculations are made in the nuclear shell model for elastic scattering, and also in the quasiparticle random-phase approximation (QRPA) and microscopic quasiparticle phonon model (MQPM) for both elastic and inelastic scattering. Using suit…
Mesonic enhancement of the weak axial charge and its effect on the half-lives and spectral shapes of first-forbidden J+↔J− decays
2018
The effects of the enhancement of the axial-charge matrix element γ5 were studied in medium heavy and heavy nuclei for first-forbidden J+↔J− decay transitions using the nuclear shell model. Noticeable dependence on the enhancement ϵMEC of the axial-charge matrix element, as well as on the value of the axial-vector coupling constant gA was found in the spectral shapes of $^{93}$Y, $^{95}$Sr, and $^{97}$Y. The importance of the spectrum of $^{138}$Cs in the determination of gA is discussed. Half-life analyses in the A≈95 and A≈135 regions were done, and consistent results gA≈0.90, 0.75, and 0.65, corresponding to the three enhancement scenarios ϵMEC=1.4, 1.7, and 2.0, were obtained. Connectio…
Dark-matter detection by elastic and inelastic LSP scattering on 129Xe and 131Xe
2008
Abstract We calculate the nuclear matrix elements involved in the elastic and inelastic scattering of the lightest supersymmetric particle (LSP) on the 129Xe and 131Xe dark-matter detector nuclei. This is the first time when both channels are addressed within the same unified microscopic nuclear framework, namely we perform large-scale shell-model calculations with a realistic two-body interaction to produce the participant nuclear wave functions. These wave functions successfully reproduce the spectroscopic data on the relevant magnetic moments and M1 decays. The tested wave functions are used to produce annual average detection rates for both the elastic and inelastic channels. It is foun…
Isospin mixing and in-beam study of non-yrast states in Co-56
2018
En el presente trabajo hemos estudiado la reacción de fusión-evaporación 56Fe(p,n gamma)56Co con un haz incidente de protones de 10 MeV en el Maier-Leibnitz-Laboratory (MLL) de la Technische Universität München (TUM, Alemania). Los rayos gamma emitidos en la desexcitación del núcleo impar-impar 56Co fueron medidos "in-beam" con cuatro detectores triples de germanio de alta resolución MINIBALL. El experimento proveyó excelentes datos en las coincidencias gamma-gamma. Un total de 223 transiciones gamma han sido observadas y colocadas en el esquema de niveles del 56Co, de las cuales 169 son gammas observadas por primera vez. Un total de 77 estados excitados han sido observador: 37 de ellos era…
Shell structure and the fluctuation of the nuclear density distribution
1984
We investigate the relation between the density-fluctuations in nuclei and their description by single-particle models, i.e. the shell model and the Hartree-Fock method; the question is whether every shell-structure necessarily leads to those fluctuations. We demonstrate the flexibility of the single-particle models by constructing a shell-model potential and an effective Hartree-Fock potential, respectively, which produce completely flat distributions without any density fluctuation; this means that “shell structure” is not sufficient an explanation for the fluctuations. Only the additional requirement that the dynamical features of nuclei are also met selects a subclass of “reasonable” po…
Gamow-Teller response in the configuration space of a density-functional-theory–rooted no-core configuration-interaction model
2018
Background: The atomic nucleus is a unique laboratory in which to study fundamental aspects of the electroweak interaction. This includes a question concerning in medium renormalization of the axial-vector current, which still lacks satisfactory explanation. Study of spin-isospin or Gamow-Teller (GT) response may provide valuable information on both the quenching of the axial-vector coupling constant as well as on nuclear structure and nuclear astrophysics.Purpose: We have performed a seminal calculation of the GT response by using the no-core configuration-interaction approach rooted in multireference density functional theory (DFT-NCCI). The model treats properly isospin and rotational sy…