566 research outputs found
Relativistic continuum-continuum coupling in the dissociation of halo nuclei
A relativistic coupled-channels theory for the calculation of dissociation
cross sections of halo nuclei is developed. A comparison with non-relativistic
models is done for the dissociation of B projectiles. It is shown that
neglecting relativistic effects leads to seizable inaccuracies in the
extraction of the astrophysical S-factor for the proton+beryllium radiative
capture reaction.Comment: 4 pages, 2 figures, version accepted for publication at Physics
Review Letter
Theoretical photo-disintegration of O
The photodisintegration of O is predicted to be dominated by 2
excitation in the vicinity of the -particle threshold.
The reaction rates of C(,)O are expected to be
determined from this reaction.Comment: 3 pages, 2 figures, Proceedings of Nuclei in the Cosmos (NIC-XIV).
19-24 June 2016, Niigata, Japa
The reaction 13C(alpha,n)16O: a background for the observation of geo-neutrinos
The absolute cross section of the C(,n)O reaction has
been measured at E = 0.8 to 8.0 MeV with an overall accuracy of 4%.
The precision is needed to subtract reliably a background in the observation of
geo-neutrinos, e.g. in the KamLAND detector.Comment: LaTex file, 13 pages including 3 ps figures. Any request to
[email protected]. Phys. Rev . C, to appea
Proton Threshold States in the 22Na(p,gamma)23Mg Reaction and Astrophysical Implications
Proton threshold states in 23Mg are important for the astrophysically
relevant proton capture reaction 22Na(p,gamma)23Mg. In the indirect
determination of the resonance strength of the lowest states, which were not
accessible by direct methods, some of the spin-parity assignments remained
experimentally uncertain. We have investigated these states with Shell Model,
Coulomb displacement, and Thomas-Ehrman shift calculations. From the comparison
of calculated and observed properties we relate the lowest relevant resonance
state at E=7643 keV to an excited 3/2+ state in accordance with a recent
experimental determination by Jenkins et al.. From this we deduce significantly
improved values for the 22Na(p,gamma)23Mg reaction rate at stellar temperatures
below T_9=0.1K.Comment: 8 pages, 4 figures, 6 table
Imaginary-time method for radiative capture reaction rate
We propose a new computational method for astrophysical reaction rate of
radiative capture process. In the method, an evolution of a wave function is
calculated along the imaginary-time axis which is identified as the inverse
temperature. It enables direct evaluation of reaction rate as a function of
temperature without solving any scattering problem. The method is tested for
two-body radiative capture reaction, , showing that it gives identical results to that calculated by the
ordinary procedure. The new method will be suited for calculation of
triple-alpha radiative capture rate for which an explicit construction of the
scattering solution is difficult.Comment: 8 pages, 7 figure
Nuclear masses, deformations and shell effects
We show that the Liquid Drop Model is best suited to describe the masses of
prolate deformed nuclei than of spherical nuclei. To this end three Liquid Drop
Mass formulas are employed to describe nuclear masses of eight sets of nuclei
with similar quadrupole deformations. It is shown that they are able to fit the
measured masses of prolate deformed nuclei with an RMS smaller than 750 keV,
while for the spherical nuclei the RMS is, in the three cases, larger than 2000
keV. The RMS of the best fit of the masses of semi-magic nuclei is also larger
than 2000 keV. The parameters of the three models are studied, showing that the
surface symmetry term is the one which varies the most from one group of nuclei
to another. In one model, isospin dependent terms are also found to exhibit
strong changes. The inclusion of shell effects allows for better fits, which
continue to be better in the prolate deformed nuclei regionComment: 10 pages, 8 tables, Proc. of the XXXIV Nuclear Physics Symposium,
January 4-7 2011, Cocoyoc, Morelos, Mexico. IOP Journal of Physics:
Conference Series (in press
Solving the two-center nuclear shell-model problem with arbitrarily-orientated deformed potentials
A general new technique to solve the two-center problem with
arbitrarily-orientated deformed realistic potentials is demonstrated, which is
based on the powerful potential separable expansion method. As an example,
molecular single-particle spectra for C + C Mg are
calculated using deformed Woods-Saxon potentials. These clearly show that
non-axial symmetric configurations play a crucial role in molecular resonances
observed in reaction processes for this system at low energy
Atomic effects in astrophysical nuclear reactions
Two models are presented for the description of the electron screening
effects that appear in laboratory nuclear reactions at astrophysical energies.
The two-electron screening energy of the first model agrees very well with the
recent LUNA experimental result for the break-up reaction , which so far defies all available theoretical models.
Moreover, multi-electron effects that enhance laboratory reactions of the CNO
cycle and other advanced nuclear burning stages, are also studied by means of
the Thomas-Fermi model, deriving analytical formulae that establish a lower and
upper limit for the associated screening energy. The results of the second
model, which show a very satisfactory compatibility with the adiabatic
approximation ones, are expected to be particularly useful in future
experiments for a more accurate determination of the CNO astrophysical factors.Comment: 14 RevTex pages + 2 ps (revised) figures. Phys.Rev.C (in production
Measurements of Gd 152 (p,γ) Tb 153 and Gd 152 (p,n) Tb 152 reaction cross sections for the astrophysical γ process
The total cross sections for the Gd152(p,γ)Tb153 and Gd152(p,n)152Tb reactions have been measured by the activation method at effective center-of-mass energies 3.47≤Ec.m.eff≤7.94 MeV and 4.96≤Ec.m.eff≤7.94 MeV, respectively. The targets were prepared by evaporation of 30.6% isotopically enriched Gd152 oxide on aluminum backing foils, and bombarded with proton beams provided by a cyclotron accelerator. The cross sections were deduced from the observed γ-ray activity, which was detected off-line by an HPGe detector in a low background environment. The results are presented and compared with predictions of statistical model calculations. This comparison supports a modified optical proton+Gd152 potential suggested earlier.Peer reviewedFinal Accepted Versio
- …