22MeV质子在^(13)C上弹性及非弹性散射微分截面的全微观分析

Full Microscopic Analysis of 22 MeV Proton Scattering from ^(13)C Nucleus

作者在9°～130°散射角范围,测量了22MeV质子在12C,13C上的弹性散射微分截面以及在13C核1/2+(3.09MeV),3/2-(3.68MeV)和5/2+(3.85MeV)激发态上的非弹性散射微分截面.对12C,13C弹性散射微分截面进行了微观光学势分析,计算结果能较好地描述实验数据.采用全微观扭曲波玻恩近似(DWBA)理论对非弹性散射实验数据进行了分析.通过小角区实验数据与理论计算结果的比较,进一步证实了13C的1/2+(3.09MeV)激发态存在中子晕结构.根据13C核1/2+(3.09MeV)激发态的其它实验结果,对1/2+(3.09MeV)态的壳模型单体密度矩阵元(OBDME)进行了修正.修正后的壳模型OBDME能较好地描述从电子散射实验得到的1/2+(3.09MeV)态的纵向和横向形状因子(formfactor)以及547MeV质子非弹性散射微分截面.另外,作者在1/2+(3.09MeV)态的质子非弹性散射实验中观察到微分截面位于120°附近的一个宽峰,该峰可能与核的π场效应(pionfieldeffect)有关.全微观DWBA计算结果大体上能给出3/2-(3.68MeV)和5/2+(3.85MeV)激发态实验数据的幅度大小,但对细节的描述还不能令人满意.作者的研究还表明了对13C核作仔细的大规模壳模型计算以及基于现代核子 核子力构造低能区密度依赖的完整的有效相互作用的必要性.

The differential cross sections of 22 MeV proton elastic scattering from 12C,13C nuclei and inelastic scattering for 1/2+(3.09MeV), 3/2-(3.68MeV) and 5/2+(3.85MeV) excitation states of 13C nucleus have been measured between 9° and 130°. The measured elastic scattering data have been compared with the results of microscopic optical potential based upon the effective nn interaction (CEG). Good agreement is obtained. The broad peak located at about 120° for 13C 1/2+(3.09MeV) state has been observed for the first time in the present proton inelastic scattering. The present experimental data for inelastic scattering were analyzed by using full microscopic distortedwave Born approximation (DWBA). From the comparison of present experimental data and theoretical results at forward angles, the authors' analysis indicates the existence of neutron halo in the 13C 1/2+(3.09MeV) excitation state. In addition, by reasonable modification of shell model wavefunction of 13C 1/2+(3.09MeV) excitation state, we can better describe the experimental form factors of (e,e′) and the experimental differential cross sections of (p,p′) at incident energy of 547 MeV. For the 13C 3/2-(3.68MeV) and 5/2+(3.85MeV) states, the full microscopic DWBA analyses can only provide a general description to the experimental data.