52 research outputs found
Pygmy dipole resonance in exotic nuclei
The evolution of the PDR strength with the neutron excess is investigated in
Sn isotopic and N=82 isotonic chains with regard to its possible connection
with the neutron skin thickness. For this purpose a recently proposed method
incorporating both HFB and multi-phonon QPM theory is applied. Analysis of the
corresponding neutron and proton dipole transition densities is presented.Comment: International Workshop on Nuclear Physics 28th Course - Radioactive
Beams, Nuclear Dynamics and Astrophysics, Ettore Majorana Center for
Scientific Cultur
Probing the Nuclear Neutron Skin by Low-Energy Dipole Modes
Dipole excitations below the neutron threshold in neutron rich Sn isotopes
are studied theoretically in the Quasiparticle-Phonon Model with HFB single
particle input. Of special interest are the low-lying two-phonon 1- states and
the Pygmy Dipole Resonance (PDR). The evolution of low-energy dipole
excitations with neutron excess is investigated over the Sn isotopic chain
including the experimentally unknown regions close to 132Sn. A dependence of
the PDR strengths and centroid energies on the neutron skin thickness is found.
Despite significant multi-phonon contributions to mean energies and transition
strengths, the PDR states retain their one-phonon character. The fragmentation
pattern is reduced with increasing neutron excess towards the N=82 shell
closure which will be of advantage for future experimental work.Comment: 4 pages, 2 figure
Pygmy Dipol Resonances as a Manifestation of the Structure of the Neutron-Rich Nuclei
Dipole excitations in neutron-rich nuclei below the neutron threshold are
investigated. The method is based on Hartree-Fock-Bogoliubov (HFB) and
Quasiparticle-Phonon Model (QPM) theory. Of our special interest are the
properties of the low-lying 1- Pygmy Resonance and the two-phonon
quadrupole-octupole 1- states in Sn-isotopes including exploratory
investigations for the experimentally unknown mass regions. In particular we
investigate the evolution of the dipole strength function with the neutron
excess. The use of HFB mean-field potentials and s.p. energies is found to
provide a reliable extrapolation into the region off stability.Comment: 8 pages, 3 figures, Proceedings of the International Conference on
Collective Motion in Nuclei Under Extreme Conditions (COMEX1), Paris, France,
10-13 June 200
Kabul Times (November 9, 1967, vol. 6, no. 184)
Recent experimental findings and theoretical approaches to the electric dipole (El) strength distribution below the particle emission threshold at shell closures are revisited. Results from photon scattering experiments are discussed and compared to predictions within the quasiparticle-phonon nuclear model. An analysis of the fine structure of the El strength is presented. Recent studies of the E1 response of light exotic nuclei are also discussed
Low-lying GT(+) strength in Co-64 studied via the Ni-64(d,He-2)Co-64 reaction
The Ni-64(d,He-2)Co-64 reaction was studied at the AGOR cyclotron of KVI, Groningen, with the Big-Bite Spectrometer and the EuroSuperNova detector using a 171-MeV deuteron beam. An energy resolution of about 110 keV was achieved. In addition to the J(pi) = 1(+) ground state, several other 1(+) states could be identified in Co-64 and the strengths of the corresponding Gamow-Teller transitions were determined. The obtained strength distribution was compared with theoretical predictions and former (n,p) experimental results and displayed a good agreement. Due to the good energy resolution, detailed spectroscopic information was obtained, which supplements the data base needed for network calculations for supernova scenarios
Low-Energy Universality in Atomic and Nuclear Physics
An effective field theory developed for systems interacting through
short-range interactions can be applied to systems of cold atoms with a large
scattering length and to nucleons at low energies. It is therefore the ideal
tool to analyze the universal properties associated with the Efimov effect in
three- and four-body systems. In this "progress report", we will discuss recent
results obtained within this framework and report on progress regarding the
inclusion of higher order corrections associated with the finite range of the
underlying interaction.Comment: Commissioned article for Few-Body Systems, 47 pp, 16 fig
Measurement of the reaction H2(e,e') at 180° close to the deuteron breakup threshold
Inclusive inelastic electron scattering off the deuteron under 180° has been studied at the S-DALINAC close to the breakup threshold at momentum transfers q=0.27fm-1 and 0.74fm-1 with good energy resolution sufficient to map in detail the spin flip M1 response, which governs the starting reaction pn›d? of big-bang nucleosynthesis over most of the relevant temperature region. Results from potential model calculations and (for q=0.27fm-1) from pionless nuclear effective field theory are in excellent agreement with the data. © 2008 The American Physical Society
Measurement of the reaction H-2(e,e(')) at 180 degrees close to the deuteron breakup threshold
WOS: 000255524300027PubMed ID: 18518283Inclusive inelastic electron scattering off the deuteron under 180 degrees has been studied at the S-DALINAC close to the breakup threshold at momentum transfers q=0.27 fm(-1) and 0.74 fm(-1) with good energy resolution sufficient to map in detail the spin flip M1 response, which governs the starting reaction pn -> d gamma of big-bang nucleosynthesis over most of the relevant temperature region. Results from potential model calculations and (for q=0.27 fm(-1)) from pionless nuclear effective field theory are in excellent agreement with the data
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