摘要:

Structure of the excited states in9Be and10Be have been theoretically explored by means of the &agr;+&agr;+nand &agr;+&agr;+n+nmicroscopic cluster model respectively. Resonance excited states in9Be and10Be are localized by solving the two‐body scattering problems of {8Be(0+, 2+, 4+)+n,5He(3/2−, 1/2−)+&agr;} and {9Be(3/2−, 1/2+, 5/2−)+n,6He(0+, 2+)+&agr;} respectively. Our models have reproduced satisfactorily the experimental low‐energy spectrum in9Be and given various resonance excited states in10Be. Our model shows that the two and three competing configurations are quite essential to reproduce the anomalous 1/2+state in9Be and the second 0+state in10Be respectively. One of these configurations has a strong core(8Be) distortion which is induced by the valence neutron and is responsible for lowering thes1/2orbit in these states. Another configuration produces a spatially extended neutron distribution outside the core like the neutron halo. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737121

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Applying the complex scaling method to calculations of strength functions of Coulomb breakup reactions, we study the structure of continuum states of two‐neutron halo nuclei6He and11Li. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737122

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Various aspects of the application of shell model approaches to cluster transfer reactions involving exotic nuclei are discussed. A scheme to calculate Spectroscopic Amplitudes for transfer reactions is given. It is calculated for a tetraneutron in8He as an example. The reduction of the t+t clustering in the6He nucleus, suggested by an experiment where transfer reactions were studied in the6He+p collision is confronted with the concept of a supermultiplet for A=6 nuclei. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737123

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

A possible issue to the nuclear waste problem is the transmutation of the long‐lived radiotoxic components of the spent fuel. The development of subcritical systems with an external neutron source, provided by a high‐energy proton beam impinging onto a spallation target are of special interest in this context. This paper describes the accelerator for such an Accelerator Driven System (ADS), studied within the European PDS‐XADS programme. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737124

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The management of long‐lived high‐level waste, such as minor actinides (MA) and long‐lived fission products (LLFP), is one of the most important issues to be solved for the utilization of the nuclear fission energy. The transmutation project of the radioactive wastes based on an accelerator driven sub‐critical (ADS) system is very attractive, since it could reduce the risk of long‐lived radioactivity and also increase the capacity of the disposal site. In the development of the ADS project networks of researchers between different fields and between different countries are crucial, since there are many scientific and technical issues, which should be studied. The activities based on these networks are discussed. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737125

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Ever since their discovery in 1960, the origin of the relatively short‐lived radionuclides, now extinct but alive in the early solar system, has been under debate. Possible scenarios are either nucleosynthetic production in stellar sources,e.g.AGB stars, Wolf‐Rayet stars, novae and supernovae, with subsequent injection into the solar nebula, or production by spallation reactions in the early solar system by energetic particles from the young sun. Here we present model calculations for the second scenario, the production of the relatively short‐lived radionuclides by solar energetic particle events in the early solar system. For successful modeling the cross sections for proton‐,3He‐, and4He‐induced reactions for all relevant nuclear reactions have to be known. In addition, the modeling depends on the relative fluence contributions of protons,3He, and4He in the solar energetic particle events as well as on their energy distribution. The ability of the model calculations to simultaneously describe the observed nuclide ratios7Be/9Be,10Be/9Be,26Al/27Al,41Ca/40Ca,53Mn/55Mn, and92Nb/93Nb is presented. Special emphasis is given to the problems arising from ill‐known cross sections for3He‐ and4He‐induced reactions. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737126

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

From the observations of the anisotropies of the Cosmic Microwave Background (CMB) radiation, the WMAP satellite has provided a determination of the baryonic density of the Universe, &OHgr;bh2, with an unprecedented precision. This imposes a careful reanalysis of the standard Big‐Bang Nucleosynthesis (SBBN) calculations. We have updated our previous calculations using thermonuclear reaction rates provided by a new analysis of experimental nuclear data constrained byR‐matrix theory. Combining these BBN results with the &OHgr;bh2value from WMAP, we deduce the light element (4He,D,3Heand7Li) primordial abundances and compare them with spectroscopic observations. There is a very good agreement with deuterium observed in cosmological clouds, which strengthens the confidence on the estimated baryonic density of the Universe. However, there is an important discrepancy between the deduced7Liabundance and the one observed in halo stars of our Galaxy, supposed, until now, to represent the primordial abundance of this isotope. The origin of this discrepancy, observational, nuclear or more fundamental remains to be clarified. The possible role of the up to now neglected7Be(d,p)2&agr; and7Be(d,&agr;)5Li reactions is considered. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737127

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

We present a calculation of nuclei propagation with energies above 1018eV in the intergalactic photon field. The calculation is based on a Monte Carlo approach for the nucleus‐photon interaction as well as the intergalactic magnetic field. We then assume that the Ultra‐High Energy Cosmic Rays (UHECR) are nuclei which are emitted from extra‐galactic point sources. Four bumps are found in the energy spectrum of the UHECR which form clusters in the distribution of their arrival directions. Based on this calculation, the energy distribution of the clustered events is discussed. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737128

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

From previous gamma‐ray missions, especially SIGMA on GRANAT and OSSE and COMPTEL on the Compton Gamma Ray Observatory we have learnt that the sky is rich in gamma‐ray line emitting objects and phenomena. Though we have certainly so far seen only the tip the iceberg, the first results are already exciting. COMPTEL produced the first‐ever all‐sky map in light of a radioactive gamma‐ray line, namely that of radioactive26Al, and OSSE mapped the inner part of the galactic plane in the light of the electron‐positron annihilation line. In addition, 1.157 MeV line emission from radioactive44Ti was detected by COMPTEL for the first time from a supernova remnant, namely Cas‐A and later possibly also from the previously unknown remnant RX JO852‐4622 as well. OSSE detected57Co line emission from SN 1987a in the Large Magellanic Cloud after56Co emission from this supernova had been detected already prior to the Compton mission, and COMPTEL saw hints of56Co line emission from the extragalactic supernova SN1991 T of type Ia. More recently COMPTEL found also hints for22Na line emission at 1.275 MeV from the classical nova N Cas 1995 and possible evidence for emission of the same line from the Galactic bulge region which may be due to unresolved novae. Already prior to these Compton observations, SIGMA provided exciting results on positron‐electron annihilation features near 511 keV from binary systems with black hole candidates (Nova Muscae and 1 E 1740‐2942). Very recently additional results, especially on the widths of the 1.809 MeV and the 511 keV annihilation lines, have been obtained by HESS I and SPI‐INTEGRAL.A review of all previous observations and the prospects of further studies with SPI‐INTEGRAL are given. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737129

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

We investigate radioactivity from the decay sequence of44Ti in a young supernova remnant SN 1987A. We perform Monte‐Carlo simulations of degradation of the nuclear lines to explain a late‐time bolometric luminosity which is estimated from optical and near‐infrared observation at 3600 days after the explosion. Assuming the distance to LMC in between 45.5 and 52.1 kpc, we have obtained the initial44Ti mass of (0.82 – 2.3) × 10−4M⊙within the current uncertainty of the physical quantities. The resulting fluxes of &ggr;‐ and hard X‐rays emerged from the44Ti decay are estimated and compared with the line sensitivity of the INTEGRAL/SPI on board and that of NeXT X‐ray satellite planned to be launched in 2010. The effect of44Ti ionization on the estimated fluxes is briefly remarked. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737130

出版商:AIP    

年代:1904

数据来源: AIP