522 research outputs found
Effective moment of inertia for several fission reaction systems induced by nucleons, light particles and heavy ions
Compound nucleus effective moment of inertia has been calculated for several
fission reaction systems induced by nucleons, light particles, and heavy ions.
Determination of this quantity for these systems is based upon the comparison
between the experimental data of the fission fragment angular distributions as
well as the prediction of the standard saddle-point statistical model (SSPSM).
For the systems, the two cases, namely with and without neutron emission
corrections were considered. In these calculations, it is assumed that all the
neutrons are emitted before reaching the saddle point.It should be noted that
the above method for determining of the effective moment of inertia had not
been reported until now and this method is used for the first time to determine
compound nucleus effective moment of inertia. Hence, our calculations are of
particular importance in obtaining this quantity, and have a significant rule
in the field of fission physics. Afterwards, our theoretical results have been
compared with the data obtained from the rotational liquid drop model as well
as the Sierk model, and satisfactory agreements were found. Finally, we have
considered the effective moment of inertia of compound nuclei for the systems
that formed similar compound nuclei at similar excitation energies.Comment: 9 pages, 2 Figures, 2 Table
Synthesis of transactinide nuclei in cold fusion reactions using radioative beams
Chances of synthesis of transactinide nuclei in cold fusion reactions
(one-neutron-out) reactions using radioactive beams are evaluated. Because
intensities of radioactive beams are in most of the cases significantly lower
than the ones of the stable beams, reactions with the highest radioactive beam
intensities for the particular elements are considered. The results are
compared with the recent ones obtained by Loveland who investigated the same
nuclei.Comment: 5 page
Fission Decay Widths for Heavy-Ion Fusion-Fission Reactions
Cross-section and neutron-emission data from heavy-ion fusion-fission
reactions are consistent with a Kramers-modified statistical model which takes
into account the collective motion of the system about the ground state; the
temperature dependence of the location of fission transition points; and the
orientation degree of freedom. We see no evidence to suggest that the nuclear
viscosity departs from the surface-plus-window dissipation model. The strong
increase in the nuclear viscosity above a temperature of ~1 MeV deduced by
others is an artifact generated by an inadequate fission model.Comment: 14 pg, 6 fig, submitted to Physical Revie
Scaling of the giant dipole resonance widths in hot rotating nuclei from the ground state values
The systematics of the giant dipole resonance (GDR) widths in hot and
rotating nuclei are studied in terms of temperature T, angular momentum J and
mass A. The different experimental data in the temperature range of 1 - 2 MeV
have been compared with the thermal shape fluctuation model (TSFM) in the
liquid drop formalism using a modified approach to estimate the average values
of T, J and A in the decay of the compound nucleus. The values of the ground
state GDR widths have been extracted from the TSFM parametrization in the
liquid drop limit for the corrected T, J and A for a given system and compared
with the corresponding available systematics of the experimentally measured
ground state GDR widths for a range of nuclei from A = 45 to 194. Amazingly,
the nature of the theoretically extracted ground state GDR widths matches
remarkably well, though 1.5 times smaller, with the experimentally measured
ground state GDR widths consistently over a wide range of nuclei.Comment: 15 pages, 4 figures, Accepted for publication in Physical Review
Activation cross-sections of proton induced reactions on Sm up to 65 MeV
Activation cross sections for proton induced reactions on Sm are presented
for the first time for
Sm(p,xn)Eu,
Sm(p,x)Sm,
Sm(p,x)Pm and
Sm(p,x)Nd up to 65 MeV. The cross sections were measured via
activation method by using a stacked-foil irradiation technique and high
resolution gamma ray spectroscopy. The results were compared with results of
the nuclear reaction codes ALICE, EMPIRE and TALYS (results taken from TENDL
libraries). Integral yields of the activation products were calculated from the
excitation functions.Comment: arXiv admin note: text overlap with arXiv:1411.716
Inconsistencies in the description of pairing effects in nuclear level densities
Pairing correlations have a strong influence on nuclear level densities.
Empirical descriptions and theoretical models have been developed to take these
effects into account. The present article discusses cases, where descriptions
of nuclear level densities are inconsistent or in conflict with the present
understanding of nuclear properties. Phenomenological approaches consider a
back-shift parameter. However, the absolute magnitude of the back-shift, which
actually corresponds to the pairing condensation energy, is generally not
compatible with the observation that stable pairing correlations are present in
essentially all nuclei. It is also shown that in the BCS model pairing
condensation energies and critical pairing energies are inconsistent for light
nuclei. A modification to the composite Gilbert-Cameron level-density
description is proposed, and the use of more realistic pairing theories is
suggested.Comment: 17 pages, 3 figure
Cross sections of deuteron induced reactions on Sm for production of the therapeutic radionuclide Sm and Sm
At present, targeted radiotherapy (TR) is acknowledged to have great
potential in oncology. A large list of interesting radionuclides is identified,
including several radioisotopes of lanthanides, amongst them Sm and
Sm. In this work the possibility of their production at a cyclotron was
investigated using a deuteron beam and a samarium target. The excitation
functions of the Sm(d,x)Sm reactions were determined for
deuteron energies up to 50 MeV using the stacked-foil technique and
high-resolution -ray spectrometry. The measured cross sections and the
contributing reactions were analyzed by comparison with results of the ALICE,
EMPIRE and TALYS nuclear reaction codes. A short overview and comparison of
possible production routes is given
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