基于色散光学模型的^(40)Ca核子散射数据计算

Calculation of nucleon scattering on ^(40)Ca based on dispersive optical model

对钙同位素核数据的研究具有重要的理论价值和应用前景,其中^(40)Ca作为天然钙最主要的同位素,是一种重要的材料核素.本文采用色散光学模型对球形核^(40)Ca的核子弹性散射数据进行计算.通过考虑色散光学模型势中实部势的非定域性以及虚部势的壳间隙结构,实现了对^(40)Ca相关核子散射数据的良好描述,其中包括中子总截面、核子弹性散射角分布以及分析本领.此外,本文计算了色散光学模型势的实部体积分,其随能量的变化图像在费米能附近出现了明显的色散峰结构.

Spherical nucleus^(40)Ca is important structural and alloy material nucleus.Based on important theoretical value and application prospect of nuclear data of calcium isotopes,nucleon-nucleus scattering data on^(40)Ca nucleus,the main isotopes of natural calcium,are calculated by using dispersive optical model(DOM).The dispersive optical model potential is defined by energy-dependent real potentials,imaginary potentials,and also by the corresponding dispersive contributions to the real potential which are calculated analytically from the corresponding imaginary potentials by using a dispersion relation that follow from the requirement of causality.By fit simultaneously scattering experimental data for neutron and proton,an isospin-dependent dispersive optical model potential containing a dispersive term is derived.This derived potential in this work considers the nonlocality in the real“Hartree-Fock”potential V_(HF)and introduces the shell gap in the definition of nuclear imaginary volume,surface and spin-orbit potentials near the Fermi energy.This dispersive optical model potential shows a good description of nucleon-nucleus scattering data on^(40)Ca nucleus up to 200 MeV including neutron total cross sections,neutron elastic scattering angular distributions,proton elastic scattering angular distributions,neutron analyzing powers and proton analyzing powers.In addition,the energy dependencies of calculated real volume integrals of dispersive optical model potential is shown,and a typical dispersive hump is seen around the Fermi energy.This dispersive hump behavior naturally obtained from dispersion relations,and allows the dispersion optical potential to get rid of energy dependent geometry,thus avoiding the use of a radius dependent on energy.