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Determination of astrophysical rates for reaction involving light unstable nuclei relevant to nucleosynthesis in novae and super novae

涉及新星和超新星核合成相关光不稳定核反应的天体物理速率的测定

基本信息

批准号：
15204025
负责人：
MOTOBAYASHI Tohru
金额：
$ 31.45万
依托单位：
RIKEN
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

Experimental results with fast RI beams provided by the RIKEN accelerator facility have been analyzed, and considerations for future studies were made.1) Proton capture reactions in the rp process studied by the Coulomb dissociation methodBased on the experimental results of the Coulomb dissociation experiments with ^<23>Al and ^<27>P beams, astrophysical reaction rates for explosive hydrogen burning processes have been determined. The critical condition in the temperature and density where the proton capture becomes faster than the positron decay was obtained. In comparison with astrophysical models for novae and X-ray bursts, it turned out that positron decays dominate in novae whereas proton capture is important in X-ray bursts.2) Reaction mechanism study on Coulomb dissociationExperiments of ^8B breakup have been performed with liquid hydrogen and helium targets in addition to a lead target, in order to extract the amount of M1, E2 and nuclear excitation components. Their results a … More re necessary to accurately extract the proton capture cross section from Coulomb dissociation. Extracted elastic scattering angular distributions were analyzed with the optical potential model. Especially, the data for the lead target were well reproduced by the potential used in the previous calculation, confirming the earlier analysis. Through discussions with theorists, existing difference between the results from the direct and Coulomb dissociation experiments may be understood by the effect of multi step processes by microscopic reaction calculations.3) Development of the method to extract M1 transition probabilityIn many reactions involved in explosive hydrogen burning, transitions with mixture of M1 and E2 components are important. Possibility of resolving the Ml component from dominant E2 in Coulomb dissociation data with precise angular distribution measurements has been considered. Based on a simulation calculation, its usefulness was examined and a new experiment has been proposed and approved at RIKEN. Less

1)用库仑解离方法研究了RP过程中的质子俘获反应。根据库仑解离实验结果，确定了爆炸氢燃烧过程的天体物理反应速率。得到了质子俘获快于正电子衰变的温度和密度的临界条件。与新星和X射线爆发的天体物理模型相比较，发现正电子衰变在新星中占主导地位，而质子俘获在X射线爆发中起重要作用。2)库仑解离反应机理研究除铅靶外，还进行了液氢和氦靶的^8B裂解实验，以提取M1、E_2和核激发成分的量。他们的结果是…为了准确地从库仑解离中提取质子俘获截面，还需要更多的数据。利用光学势模型分析了提取的弹性散射角分布。特别是，前一次计算中使用的势能很好地再现了铅目标的数据，证实了早先的分析。通过与理论工作者的讨论，直接解离实验和库仑解离实验结果之间存在的差异可以通过微观反应计算的多步过程的影响来理解。3)提取M1跃迁几率的方法的发展在许多涉及爆炸性氢燃烧的反应中，M1和E2组分的混合物的跃迁是重要的。考虑了用精确的角分布测量从库仑解离数据中的主要E_2中分辨M_1组分的可能性。在模拟计算的基础上，对其有效性进行了检验，并提出了一个新的实验方案，并在理研中心得到了批准。较少