Electric and magnetic dipole strength in Sn112,114,116,118,120,124
Electric and magnetic dipole strength in Sn112,114,116,118,120,124
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Sn112,114,116,118,120,124中的电偶极子和磁偶极子强度
DOI：
10.1103/physrevc.102.034327
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发表时间：
2020
影响因子：
3.1
通讯作者：
Noj
中科院分区：
文献类型：
--
作者：
Bassauer S.;von Neumann-Cosel P.;Reinhard P.-G.;Tamii A.;Adachi S.;Bertulani C. A.;Chan P. Y.;D'Alessio A.;Fujioka H.;Fujita H.;Fujita Y.;Gey G.;Hilcker M.;Hoang T. H.;Inoue A.;Isaak J.;Iwamoto C.;Klaus T.;Kobayashi N.;Maeda Y.;Matsuda M.;Nakatsuka N.;Noj
背景：人们对电偶极子强度分布重新产生了兴趣，原因包括与对称能性质相关的偶极子极化率的提取和中子表皮厚度的测量，对中子过剩核中低能量强度结构的理解，以及等矢量巨偶极子共振（IVGDR）系统的建立。在几百MeV的能量和非常向前的角度下，质子的非弹性散射已被建立为研究原子核中电和磁偶极子强度分布的工具。目的：系统地研究稳定等质量锡同位素链中的电偶极子和磁偶极子强度分布。方法：在大阪核物理研究中心进行非弹性质子散射实验，以295 mev光束覆盖实验室角度，激发能量为mev。利用多极分解分析（MDA）分别提取激发态和激发态的截面，然后分别用“虚光子法”和“单位截面法”将其转换为简化的跃迁概率。包括对实验未覆盖的高激发能区域的理论辅助校正，电偶极子极化率由强度分布确定。结果：在IVGDR的能量区，由光强分布得到的总光吸收截面与以往的实验结果有显著差异。用洛伦兹参数化从目前的数据推断出的IVGDR宽度显示出大约4.5 MeV的恒定值，而不是以前工作中观察到的同位素之间的大变化。IVGDR质心能量很好地符合其质量依赖的经验系统学的期望。此外，还研究了IVGDR能量与体物质性质的关系。中子阈值以下的强度与实验结果相当一致，在6 - 7 MeV之间的能量区域也发现了等标强度。在较高的激发能量下，观察到较大的差异，表明激发态具有较小的基态分支比的不同性质。在所有被研究的原子核中，等矢量自旋强度在6 ~ 12mev之间分布广泛。结论：目前的结果有助于解决各种核结构问题，包括IVGDR的能量和宽度的系统化，核中低能量强度的结构，旨在系统描述核图上偶极极化率的能量密度泛函（edf）的新约束，由此可以推导对称能的性质，以及重核中等矢量自旋强度的系统化。
Background:There is renewed interest in electric dipole strength distributions for a variety of reasons including the extraction of the dipole polarizability related to properties of the symmetry energy and a measure for the neutron skin thickness, understanding the structure of low-energystrength in nuclei with neutron excess, and establishing the systematics of the isovector giant dipole resonance (IVGDR). Inelastic proton scattering at energies of a few hundred MeV and very forward angles includinghas been established as a tool for the study of electric and magnetic dipole strength distributions in nuclei.Purpose:The present work aims at a systematic investigation of the electric and magnetic dipole strength distributions in the chain of stable even-mass tin isotopes.Methods:Inelastic proton scattering experiments were performed at the Research Center for Nuclear Physics, Osaka, with a 295-MeV beam covering laboratory anglesand excitation energiesMeV. Cross sections due toandexcitations were extracted with a multipole decomposition analysis (MDA) and then converted to reduced transition probabilities with the “virtual photon method” forand the “unit cross section method” forexcitations, respectively. Including a theory-aided correction for the high-excitation-energy region not covered experimentally, the electric dipole polarizability was determined from thestrength distributions.Results:Total photoabsorption cross sections derived from theandstrength distributions show significant differences compared to those from previousexperiments in the energy region of the IVGDR. The widths of the IVGDR deduced from the present data with a Lorentz parametrization show an approximately constant value of about 4.5 MeV in contrast to the large variations between isotopes observed in previous work. The IVGDR centroid energies are in good correspondence to expectations from empirical systematics of their mass dependence. Furthermore, a study of the dependence of the IVGDR energies on bulk matter properties is presented. Thestrengths below neutron threshold show fair agreement with results fromexperiments onin the energy region between 6 and 7 MeV, where also isoscalarstrength was found for. At higher excitation energies, large differences are observed, pointing to a different nature of the excited states with small ground-state branching ratios. The isovector spin-strengths exhibit a broad distribution between 6 and 12 MeV in all studied nuclei.Conclusions:The present results contribute to the solution of a variety of nuclear structure problems including the systematics of the energy and width of the IVGDR, the structure of low-energystrength in nuclei, new constraints to energy density functionals (EDFs) aiming at a systematic description of the dipole polarizability across the nuclear chart, from which properties of the symmetry energy can be derived, and the systematics of the isovector spin-strength in heavy nuclei.