Search results for "nuclear structure"
showing 10 items of 401 documents
Nuclear weak response from the combined study of beta-decay and charge-exchange reaction
2009
Studying the weak nuclear response, especially the Gamow-Teller (GT) transitions, of stable as well as unstable pf-shell nuclei, is one of the key issues in nuclear and astro-nuclear physics. We study the decay half-lives and the GT transitions starting from Tz = ±1 and ±2 mirror nuclei, respectively, by means of β decays and complementary hadronic (3 He , t) charge-exchange reactions. Under the assumption that isospin is a good quantum number, symmetry is expected for mirror nuclei and the GT transitions starting from the mirror nuclei. The half-lives and branching ratios and the measured strength distributions of GT transitions are compared and also combined for the understanding of the …
Nuclear symmetry energy and neutron skins derived from pygmy dipole resonances
2007
By exploiting Coulomb dissociation of high-energy radioactive beams of the neutron-rich nuclei $^{129\ensuremath{-}132}\mathrm{Sn}$ and $^{133,134}\mathrm{Sb}$, their dipole-strength distributions have been measured. A sizable fraction of ``pygmy'' dipole strength, energetically located below the giant dipole resonance, is observed in all of these nuclei. A comparison with available pygmy resonance data in stable nuclei ($^{208}\mathrm{Pb}$ and $N=82$ isotones) indicates a trend of strength increasing with the proton-to-neutron asymmetry. On theoretical grounds, employing the RQRPA approach, a one-to-one correlation is found between the pygmy strength and parameters describing the density d…
Relativistic Coulomb excitation of Kr 88
2016
International audience; To investigate the systematics of mixed-symmetry states in N=52 isotones, a relativistic Coulomb excitation experiment was performed during the PreSPEC campaign at the GSI Helmholtzzentrum für Schwerionenforschung to determine E2 transition strengths to 2+ states of the radioactive nucleus $^{88}$Kr. Absolute transition rates could be measured towards the first and third 2+ states. For the latter a mixed-symmetry character is suggested on the basis of the indication for a strong M1 transition to the fully symmetric 21+ state, extending the knowledge of the N=52 isotones below Z=40. A comparison with the proton-neutron interacting boson model and shell-model predictio…
Angular momentum projection of cranked Hartree-Fock states: Application to terminating bands inA~44nuclei
2007
We present the first systematic calculations based on the angular-momentum projection of cranked Slater determinants. We propose the Iy --> I scheme, by which one projects the angular momentum I from the 1D cranked state constrained to the average spin projection of =I. Calculations performed for the rotational band in 46Ti show that the AMP Iy --> I scheme offers a natural mechanism for correcting the cranking moment of inertia at low-spins and shifting the terminating state up by ~2 MeV, in accordance with data. We also apply this scheme to high-spin states near the band termination in A~44 nuclei, and compare results thereof with experimental data, shell-model calculations, and res…
Structure of 68As studied via the 12C(58Ni,pn) reaction
1998
Excited states of As-68 nucleus were populated through the C-12(Ni-58,pn) reaction and investigated by in-beam gamma-spectroscopic methods. The NORDBALL detector array equipped with charged particle and neutron detectors was used to detect the evaporated particles and gamma-rays. The level scheme of As-68 was constructed on the basis of gamma gamma-coincidence relations up to 6 MeV excitation energy and J(pi) = (15(+)). The structure of the nucleus is discussed in the framework of the interacting boson-fermion-fermion model. The states below 2.3 MeV are described as members of proton-neutron-phonon multiplets. (C) 1998 Elsevier Science B.V.
Nuclear structure “southeast” ofPb208: Isomeric states inHg208andTl209
2009
The nuclear structure of neutron-rich N>126 nuclei has been investigated following their production via relativistic projectile fragmentation of a E/A=1 GeV U-238 beam. Metastable states in the N=128 isotones Hg-208 and Tl-209 have been identified. Delayed gamma-ray transitions are interpreted as arising from the decay of I-pi=(8(+)) and (17/2(+)) isomers, respectively. The data allow for the so far most comprehensive verification of the shell-model approach in the region determined by magic numbers Z 126.
The nuclear structure of $^{223}$Fr
1991
Abstract The γ-rays following the β− decay of 223Rn have been investigated by means of γ-ray singles including multispectrum analysis, and γγ-coincidence measurements using Ge detectors. Multipolarities of 38 transitions in 223Fr have been established by measuring conversion electrons with a mini-orange electron spectrometer. Most of the observed transitions could be placed in a level scheme comprising 53 excited states of 223Fr. The level structure is interpreted in terms of K π = 3 2 ± and 1 2 ± parity doublet bands, and a second K π = 3 2 ± higher-lying parity doublet. The experimental data are compared with the theoretical predictions of the reflection-asymmetric rotor model.
The nuclear structure of 229Th
2002
Abstract The γ -rays following the β − decay of 229 Ac have been investigated by means of γ -ray singles and γγ -coincidence measurements using Ge detectors. Multipolarities of 40 transitions in 229 Th have been established by measuring conversion electrons with a mini-orange electron spectrometer. The half-lives of the 146.35, 164.53 and 261.96 keV levels have been measured using the advanced time delayed βγγ (t) method. The low-lying states in 229 Th and observed transition rates have been interpreted within the quasiparticle–phonon model with inclusion of Coriolis coupling. Two octupole correlated parity partner bands, with K π =5/2 ± and K π =3/2 ± , were identified in 229 Th.
NUCLEAR-STRUCTURE EFFECTS ON DOUBLE BETA DECAYS TO 0+ STATES IN 76Ge
2011
Neutrinoless double beta (0νββ) decay of 76 Ge to the ground state and first excited 0+ state in 76 Se is discussed in terms of the associated nuclear matrix elements. The effects arizing from the size of the single-particle model space and the occupancies of the individual orbits are discussed in the framework of the (higher) quasiparticle random-phase approximation with effective, G -matrix-derived nuclear forces. It is found that the orbital occupancies play a role for the size of the nuclear matrix element. Contrary to the ground-state transition the transition to the first excited 0+ state does not depend sensitively on the size of the model space.
Coherent and incoherent η-photoproduction from nuclei
1991
Abstract Elastic and inelastic η-photoproduction from complex nuclei is studied in a distorted-wave impulse approximation (DWIA) framework. The elementary operator is obtained by using a dynamical model which employs the reactions π N→ π N, π N→ ππ N and π − p→ η n to fix the hadronic vertex as well as the isobar propagators and the process γ N→ π N to constrain the electromagnetic vertex. The nuclear structure input for the inelastic transitions has been extracted from electron-scattering form factors. The η final-state interaction has been included via a simple optical potential using the ηN t -matrix as an input. We find that coherent η-production is dominated by the D 13 (1520) isobar w…