利用质子非弹性散射研究13C的第一1/2^+激发态晕结构

In this project, we have measured the differential cross sections of 22 MeV proton elastic scattering from 12,13C nuclei and inelastic scattering for 1/2+(3.09MeV), 3/2-(3.68MeV) and 5/2+(3.85MeV) excitation states of 13C nucleus between 90 and 1300. The measured elastic scattering data have been compared with the result of microscopic optical potential based upon a density-dependent NN effective interaction. Good agreement is obtained. The present experimental data were analyzed by using microscopic distorted-wave Born approximation. From the comparison of present experimental data and theoretical results at forward angles, our analysis indicates the existence of neutron halo in the 13C 1/2+(3.09MeV) excitation state. In addition, by reasonable modification of shell model wavefunction of 13C 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. In this project, a broad peak located at ~1200 for 13C 1/2+(3.09MeV) state has been observed for the first time in the present proton inelastic scattering, indicating that the broad peak located at ~1200 is a general feature for transitions, which involve the isovector 0+?0- component. This broad peak is very likely associated with the effects of the pion field in nuclei. The differential cross sections of 3/2-(3.68MeV) and 5/2+(3.85MeV) states were also analyzed by using microscopic distorted-wave Born approximation. The results obtained in this project further show the halo universality, and also indicate the neceseity for a detailed large-scale shell model calculation for the structure of 13C nucleus and construction of a reliable, complete density-dependent effective interaction in low-energy regions based upon the modern nucleon-nucleon potentials.

{13}C核是稳定核，它的第一1/2^+(E_x=3.09Me V)激发态的低能中子^{12}C(n,g)^{13}C(1/2}^+_1直接俘获截面异常增大，可能源于此激发态的中子晕结构，并为核天体物理所关心。本研究利用22MeV质子非弹性散射，测量其散射微分截面，并采用微观DWBA理论研究此激发脑谓峁梗酝几鲈蔚男巫醇按笮。⒂兄诙栽谓峁挂话阈晕侍?halo universality)的探