124 research outputs found
Quantum Monte Carlo calculations of nuclei
We report on quantum Monte Carlo calculations of the ground and low-lying
excited states of nuclei using realistic Hamiltonians containing the
Argonne two-nucleon potential alone or with one of several
three-nucleon potentials, including Urbana IX and three of the new Illinois
models. The calculations begin with correlated many-body wave functions that
have an -like core and multiple p-shell nucleons, -coupled to the
appropriate quantum numbers for the state of interest. After
optimization, these variational trial functions are used as input to a Green's
function Monte Carlo calculation of the energy, using a constrained path
algorithm. We find that the Hamiltonians that include Illinois three-nucleon
potentials reproduce ten states in Li, Be, Be, and B with
an rms deviation as little as 900 keV. In particular, we obtain the correct
3 ground state for B, whereas the Argonne alone or with
Urbana IX predicts a 1 ground state. In addition, we calculate isovector
and isotensor energy differences, electromagnetic moments, and one- and
two-body density distributions.Comment: 28 pages, 12 tables, 7 figure
Mass splittings of nuclear isotopes in chiral soliton approach
The differences of the masses of nuclear isotopes with atomic numbers between
\~10 and ~30 can be described within the chiral soliton approach in
satisfactory agreement with data. Rescaling of the model is necessary for this
purpose - decrease of the Skyrme constant by about 30%, providing the "nuclear
variant" of the model. The asymmetric term in Weizsaecker-Bethe- Bacher mass
formula for nuclei can be obtained as the isospin dependent quantum correction
to the nucleus energy. Some predictions for the binding energies of neutron
rich nuclides are made in this way, from, e.g. Be-16 and B-19 to Ne-31 and
Na-32. Neutron rich nuclides with high values of isospin are unstable relative
to strong interactions. The SK4 (Skyrme) variant of the model, as well as SK6
variant (6-th order term in chiral derivatives in the lagrangian as solitons
stabilizer) are considered, and the rational map approximation is used to
describe multiskyrmions.Comment: 16 pages, 10 tables, 2 figures. Figures are added and few misprints
are removed. Submitted to Phys. Atom. Nucl. (Yad. Fiz.
Measurement of alpha and neutron decay widths of excited states of C-14
The 12C 16O,14O 14C reaction was studied at a beam energy of 234 MeV. The 14O ejectile was detected by a Q3D spectrometer at forward angles. The energies and angles of the excited 14C recoil break up fragments were measured in coincidence with the 14O ejectile using a double sided silicon strip detector array at backward angles. A complete kinematic reconstruction of the reaction was performed to reconstruct the 14C rightarrow 10Be and 14C rightarrow 13 n decay channels and the branching ratios and widths of these decays were calculated. Theoretical decay branches were calculated using barrier penetrability factors and were compared to the measured ratios to provide information on the spins, parities, and configurations of the states. Neutron emission was found to be favored for the 11.73, 12.96, 14.87,16.72, and 18.6 MeV states. The 14.87, 18.6, and 21.4 MeV states were found to have a considerable width for decay and are candidates for the three bodied molecular cluster structure of 14
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