摘要:

Nuclear reaction rates are obviously quantities of fundamental importance in nuclear astrophysics. Important effort has been devoted in the last decades to measure reaction cross sections and many experimental compilations have now become available. Despite such effort, many nuclear astrophysics applications still require the use of theoretical predictions to estimate experimentally unknown rates. Most of the nuclear ingredients in the calculations of reaction rates need to be extrapolated in an energy or/and mass domain out of reach of laboratory simulations. In addition, important astrophysical applications (in particular the r‐ or p‐processes of nucleosynthesis) often involve a large number (thousands) of unstable nuclei, so that only global approaches can be used. For these reasons, when the nuclear ingredients to the reaction models cannot be determined from experimental data, use is made preferentially of microscopic or semi‐microscopic global predictions based on sound and reliable nuclear models which, in turn, can compete with more phenomenological highly‐parametrized models in the reproduction of experimental data.The International Atomic Energy Agency (IAEA) addressed recently through a Coordinated Research Project on the Reference Input Parameter Library (RIPL) the difficult task of collecting, evaluating and recommending the vast amounts of various nuclear parameters of relevance in cross section calculations. The RIPL project is targeted at users of nuclear reaction codes and, in particular, at nuclear data evaluators for applications as large as energy production, accelerator driven waste incineration, production of radioisotopes for therapy and diagnostics, charged particle beam therapy, material analysis and astrophysics. A brief overview of the nuclear input parameters recommended by the RIPL is presented.Simultaneously, the need to develop more microscopic input parameters has led to new developments that have been compiled in the Brussels Nuclear Astrophysics Library, known as BRUSLIB. The content of the BRUSLIB library is described, with a special emphasis on the latest results concerning the determination of ground state properties within the Hartree‐Fock‐Bogoliubov approach. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737131

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

In nuclear astrophysics, optical model potentials play an important role, both in the nucleosynthesis models, and in the interpretation of astrophysics related nuclear physics measurements. The challenge of nuclear astrophysics resides in the fact that it involves many nuclei far from the stability line, implying than very few (if any) experimental results are available for these nuclei. The answer to this challenge is a heavy reliance on microscopic optical models with solid microscopic physics foundations that can predict the relevant physical quantities with good accuracy. This use of microscopic information limits the likelihood of the model failing spectacularly (except if some essential physics was omitted in the modeling) when extrapolating away from the stability line, in opposition to phenomenological models which are only suited for interpolation between measured data points and not for extrapolating towards unexplored areas of the chart of the nuclides.We will show how these microscopic optical models are built, how they link to our present knowledge of nuclear structure, and how they affect predictions of nuclear astrophysics models and the interpretation of some key nuclear physics measurements for astrophysics. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737132

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Large‐scale QRPA calculations of the E1‐strength are performed on top of HFB calculations in order to derive the radiative neutron capture cross sections for the whole nuclear chart. The spreading width of the GDR is taken into account by analogy with the second‐RPA (SRPA) method. It is shown that the present model allows to constrain the effective nucleon‐nucleon interaction with the GDR data and to provide quantitative predictions of dipole strengths. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737133

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

We calculate fission barriers with the Skyrme‐Hartree‐Fock‐Bogoliubov plus particle number projection (SHFB+PLN) method, using a Skyrme force fitted to essentially all the nuclear mass data with the same method. The reflection asymmetry is introduced to study the lowering of the outer barrier of three selected nuclei. We discuss the feasability of performing large‐scale SHFB+PLN fission‐barrier calculations, i.e. for about 2000 nuclei of astrophysical interest. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737134

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Major astrophysical applications involve a huge number of exotic nuclei. An important effort has been devoted during the last decades to the measurements of the masses and &bgr;‐decay rates of very neutron‐rich nuclei at RIB facilities. However, most of them cannot be synthesised in terrestrial laboratories and only theoretical predictions can fill the gap. We concentrate mainly on the &bgr;‐decay rates needed for the stellar r‐process modeling and for performing the RIB experiments. The continuum QRPA approach based on the self‐consistent ground state description in the framework of the density functional theory is briefly described. The model for the large‐scale calculations of total &bgr;‐decay half‐lives accounts for the Gamow‐Teller and first‐forbidden transitions. Due to the shell configuration effect, the first‐forbidden decays have a strong impact on the total half‐lives of the r‐process relevant nuclei at N=126, Z=60–70. The performance of existing global models for the nuclides near the r‐process paths at N=126 is critically analyzed and confronted with the recent RIB experiments in the region “east” of208Pb . The possible role of neutrino nucleosynthesis is exemplified by the production of rare isotope138La via the neutrino process. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737135

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

We briefly review the short contributions and discussions called forth in a “round table” time‐slot following the formal presentations on nuclear data needs. The subjects covered are: microscopic model investigations of nuclear fissions, experimental and theoretical aspects of fixing masses and half‐lives of nuclei far off stability, and measurements of photo‐disintegration cross sections needed for nucleosynthesis studies. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737136

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

A systematic study aiming at establishing an extended cross‐section database of mainly proton capture reactions of nuclei in the Se‐Sb region is presented. Such a database is required to perform a validity test of the Hauser‐Feshbach (HF) calculations in the medium‐mass region that will enable to investigate the impact of nuclear physics uncertainties onp‐nuclei abundance calculations. The results of this systematic work as well as a comparison of all existing cross‐section data with the predictions of the HF theory are presented. Several aspects of all the experiments performed so far including a recent in‐beam cross section measurement of the92Mo(&agr;, &ggr;)96Ru reaction are outlined. The question of whether the experimental information obtained so far is sufficient to draw final conclusions is discussed. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737137

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The evolution of experiments with radioactive beams in nuclear astrophysics is reviewed, regarding the techniques (beams and detectors), the astrophysical consequences, the status of indirect methods. Perspectives are outlined. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737138

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

&ggr;‐ray beams at synchrotron radiation facilities will give us unprecedented opportunities to study photonuclear reactions of astrophysical interest. We report our photonuclear reaction studies and give a prospect of a fertile research field to be pioneered in the next 5 years. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737139

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

A low‐energy radioactive‐ion beam separator based on an in‐flight technique was developed at CNS, University of Tokyo and was installed at RIKEN. Using the separator, experiments of the elastic resonance scattering of11C+p,12N+p, and23Mg+p were performed to study resonance levels in12N,13O, and24Al, respectively. New information on spin‐parities and widths for these levels may help understand stellar (p,&ggr;) reaction rates. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737140

出版商:AIP    

年代:1904

数据来源: AIP