Experimental investigations and R-matrix analysis of low-lying levels in (5)He and (5)Li.

摘要

The particle-unstable nuclei /sup 5/He and /sup 5/Li have been studied via the /sup 4/He(/sup 7/Li, /sup 6/Li)/sup 5/He and /sup 4/He(/sup 7/Li, /sup 6/He)/sup 5/Li stripping reactions at beam energies of 50 MeV and the /sup 6/Li(/sup 12/C, /sup 13/N) /sup 5/Li pickup reactions at 90 MeV. The experimental data clearly demonstrate a dependence of the lineshapes on the method of production of the mass-5 nuclei (in this case pickup or stripping). The observed lineshapes were analysed using the R-matrix formalism in a two-level approximation for each J/sup (pi)/ value, with parameter values deduced from fits to the available /sup 4/He+nucleon scattering data. Properties of the lowest 3/2/sup -/ and 1/2/sup -/ states of /sup 5/He and /sup 5/Li, observed via direct reactions, are deduced from the parameter values. These properties; are compared with results from earlier experimental analyses and the inferred properties of positive-parity states are compared with the results of recent shell-model calculations. (Atomindex citation 20:051075)