Marc Rayet

A compilation of charged-particle induced thermonuclear reaction rates

Low-energy cross section data for 86 charged-particle induced reactions involving light (1 less than or equal to Z less than or equal to 14), mostly stable, nuclei are compiled. The corresponding Maxwellian-averaged thermonuclear reaction rates of relevance in astrophysical plasmas at temperatures in the range from 10(6) K to 10(10) K are calculated. These evaluations assume either that the target nuclei are in their ground state, or that the target states are thermally populated following a Maxwell-Boltzmann distribution, except in some cases involving isomeric states. Adopted values complemented with lower and upper limits of the rates are presented in tabular form. Analytical approximations to the adopted rates, as well as to the inverse/direct rate ratios, are provided

The puzzle of the synthesis of the rare nuclide

The calculations of the p -process in the O/Ne layers of Type II supernovae are quite successful in reproducing the solar system content of p-nuclides. They predict, however, a signicant underproduction of the rare odd-odd nuclide 138 La. A model for the explosion of a 25 M star with solar metallicity is used to suggest that e-captures on 138 Ba may well be its most ecient production mechanism. The responsibility of an inadequate prediction of the 138 La and 139 La photodisintegration rates in the too low production of 138 La is also examined quantitatively. A detailed discussion of the theoretical uncertainties in these rates suggest that the required rate changes are probably too high to be fully plausible. Their measurement would be most welcome. They would help disentangling the relative contributions of thermonuclear and neutrino processes to the 138 La production.

\mathsf{^{138}}

Abstract The spherical Skyrme Hartree-Fock formalism has been used to derive an effective A -nucleon interaction of the Skyrme type. This interaction is required to fit the ground-state binding energies of 5ΛHe, 13Λ C and 16ΛO as well as the energy difference between the 16ΛO ground state and its excited state at BΛ = 2.5 MeV where the Λ-particle is assumed to be excited from the s- to the p-shell. The three-body ΛNN interaction is found to be correlated to this shell excitation energy. Having assumed for simplicity the Λ -nucleon spin-orbit force to be zero, a convenient parametrization is obtained, which provides also good results for other hypernuclear data. However, it is not possible to retain any analogy between the ΛN and the NN effective interactions.

La

An extension of the Skyrme--Hartree--Fock formalism is proposed for calculating ..lambda.. binding energies (B/sub ..lambda../) in hypernuclei throughout the periodic table. The calculation includes the self-consistent nuclear polarization by the ..lambda.. hyperon. Realistic estimates for ground state B/sub ..lambda../s are obtained with a simple effective ..lambda..N force and are compared with a ..lambda..--nucleus potential model. The ..lambda.. particle excitation spectra have also been calculated. They are discussed in the context of strangeness analog state formation, and the emphasis is put on the symmetry between ..lambda.. and nuclear states. (AIP)

Skyrme parametrization of an effective Λ-nucleon interaction

The high-entropy α-rich freeze-out of neutron-rich nuclei suggested by Woosley and Hoffman and the subsequent formation of r-nuclides are studied in the framework of a recent supernova model. The calculations are performed with the help of a single reaction network that is able to describe the establishment of the nuclear statistical equilibrium, the charged-particle reaction freeze-out, and the subsequent neutron captures and β-decays that produce the r-nuclides. We analyze the effect of using various models for the nuclear binding energies, and in particular the new Extended Thomas-Fermi plus Strutinsky Integral method and the finite-range droplet model

Self-consistent calculations of hypernuclear properties with the Skyrme interaction

He-accreting white dwarfs with sub-Chandrasekhar mass are revisited. The impact of the use of an extended reaction network on the predicted energy production and characteristics of the detonating layers is studied. It is shown that the considered scenario can be the site of an

Neutron-rich α-rich freeze-out and the r-process in the high-entropy neutrino-energized supernova bubble

\alpha p

He-detonation in sub-chandrasekhar co white dwarfs: a new insight into energetics and p-process nucleosynthesis

-process combined with a p -process and with a variant of the rp -process we refer to as the pn -process. We define the conditions under which the derived distribution of the abundances of the p -nuclides in the ejecta, including the puzzling light Mo and Ru isotopes, mimics the solar-system one.

Direct determination of photodisintegration cross sections and the p-process

Abstract Photon-induced reactions play a key role in the nucleosynthesis of heavy neutron-deficient nuclei, the so-called p-nuclei. In this paper we review the present status of experiments on photon-induced reactions at energies of astrophysical importance and their relevance to p-process modeling.

A microscopic approach to Λ9Be

Abstract The binding energy of the hypernucleus Λ 9 Be is calculated by the variation principle with a determinantal single particle wave function which exhibits the α-α-Λ structure of Λ 9 Be. Effective N-N forces are used and an effective Λ-N force is determined from the Λ 5 He binding energy. Size and shape polarization of the α particles is determined by the variational procedure. Two orbitals of opposite parity are considered for the Λ particle. Their energies are discussed as well as the nuclear distortions induced by the Λ particle.