摘要:

Photon‐induced reactions during the astrophysicalp‐ (or &ggr;‐) process occur at typical temperatures of 1.8 ⩽T9⩽ 3.3. Experimental data of (&ggr;,n), (&ggr;,p), or (&ggr;,&agr;) reactions — if available in the relevant energy region — cannot be used directly to measure astrophysical (&ggr;,n), (&ggr;,p), or (&ggr;,&agr;) reaction rates because of the thermal excitation of target nuclei at these high temperatures. Usually, statistical model calculations are used to predict photon‐induced reaction rates. The relations between experimental reaction cross sections, theoretical predictions, and astrophysical reaction rates will be critically discussed. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737151

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Fission potential‐energy surfaces are calculated from a microscopic Hartree‐Fock‐Bogoliubov description of the deformed nucleus, fully constrained in the three deformation coordinates (c, h, &agr;). The dynamical fission paths along the multidimensional symmetric and asymmetric deformation space are determined by applying the classical least action principle. The resulting dynamical fission barriers and spontaneous fission half‐lives are compared with the experimental values for240Pu. Furthermore, microscopic calculations of fission barriers and nuclear level densities are used to obtain neutron‐induced fission cross sections. The results for the actinides are compared with existing experimental data in the low energy region ≈100 keV relevant to the r‐process nucleosynthesis. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737152

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

In the p‐process production of180Tam, not only photo‐production cross sections of181Ta(&ggr;,n)180Ta but also photo‐destruction cross sections of180Tam(&ggr;,n)179Ta are needed. We propose to measure the destruction cross section with high‐energy synchrotron radiation generated from a 10 tesla super‐conducting wiggler at SPring‐8. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737153

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Photodisintegration cross sections were measured for deuterium with Laser Compton scattering &ggr; beams at E&ggr;= 2.3 – 4.6 MeV. The experimental evaluation ofR(E) =Na&sgr;vfor the p(n,&ggr;)D reaction was performed in the energy region relevant to big bang nucleosynthesis (BBN) by using the present data combined with the preceding data. The result confirms the past theoretical evdaluation with 6&percent; uncertainty. The reaction rate for the p(n,&ggr;)D reaction is presented for the BBN in the precision era. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737154

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

We have analyzed cold fusion reactions, especially, (HI(Heavy‐Ion), xn) reactions with208Pb target series. The ratio af/anused in the statistical model is determined by fitting experimental data of &Ggr;n/&Ggr;totalforZ=102 and the extrapolative use is made forZ>103. Theoretical predictions for excitation functions in208Pb(50Ti,51V,54Cr,55Mn,58Fe,59Co,65Cu,70Zn, xn) reactions are compared with experiments. We found that peak positions of (HI, xn) reactions except for the sub‐barrier fusion enhancement effect stay almost constant when we increase theZ‐number of compound nucleus fromZ=104 toZ=110. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737155

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Recent measurements of total8B solar neutrino flux comprising neutrinos of different flavors account for all the missing high energy8B solar neutrinos and agree well with Standard Solar Model (SSM) calculations. Since only electron neutrinos should be produced at the center of the sun, so the observations of neutrinos of different flavors provide evidence in the support of neutrino flavor oscillation. However at present, the uncertainty on the measured8B solar neutrino flux is over 10&percent; and that on the predicted flux from SSM calculations is also over 10&percent;. So it is important to improve upon the accuracy of both the measured and predicted8B solar neutrino fluxes for a precise comparison between them. Such comparison should be important for better understanding of both neutrino and solar physics. The most uncertain parameter in the calculation of8B solar neutrino flux using SSM is7Be(p,&ggr;)8B reaction rate at solar Gammow energy. This reaction rate is usually represented by S17(0) factor and so high precision measurement of S17(0) factor is required. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1737156

出版商:AIP    

年代:1904

数据来源: AIP