Structure of sup 14 C Via Elastic and Inelastic Neutron Scattering from sup 13 C: Measurement, R-Matrix Analysis, and Shell Model Calculations

摘要

The specific purpose of this work is to provide a better understanding of the sup 14 C level structure; the general purpose is to provide the details for using shell model calculations in R-matrix analyses. Using the TOF facilities of the Ohio University Accelerator Laboratory, the elastic and first 3 inelastic differential scattering cross sections for sup 13 C + n were measured at 69 energies for 4.5 less than or equal to E/sub n/ less than or equal to 11 MeV. A multiple scattering code was developed which provided a simulation of the experimental scattering process allowing accurate corrections to the small inelastic data. The integrated sup 13 C(n, alpha ) sup 10 Be cross section is estimated. The sequential 2n-decay of sup 14 C states populated by sup 13 C + n was observed. A shell model code was developed. Normal and nonnormal parity calculations were made for the lithium isotopes using a new two-body interaction. The results for sup 5 Li predict the 2s/sub 1/2/ and 1d/sub 5/2/ single-particle states to be located below the 3/2 sup + state. Similar calculations were made for sup 13 C, sup 13 N, and sup 14 C. Results for sup 13 C and sup 13 N show for E/sub x/ < 10 MeV the Thomas-Ehrman shifts are related to the 2s/sub 1/2/ single-particle energies. For sup 7 Li and sup 14 C, 2 h-bar omega calculations were done. Shell model calculations generated the R-matrix parameters for the elastic and first 3 inelastic channels of sup 13 C + n. After adjusting some energies, the predicted structure generally agrees with experiment for E/sub n/ < 4 MeV. Previous elastic sup 13 C + n data were refit to replace R sub 0 background terms by more realistic broad states and to get better agreement with model calculations. R-matrix fitting of the full data set produced new sup 14 C level information. For E/sub n/ > 4 MeV (E/sub x/ > 12 MeV), 5 states are given definite J/sup pi / assignments; 3, tentative assignments. 122 refs., 91 figs., 30 tabs. (ERA citation 12:029635)