Structure studies of 7Li, 8Li, 11B and 12B from elastic scattering of neutrons

The Ohio University tandem accelerator was employed to produce neutrons via the reaction T(p,n) 3He in the range 4 MeV less than or equal to E/sub n/ less than or equal to 8 MeV where only sparse scattering data exist for several of the light nuclei. Differential elastic scattering cross sections were measured in this range for 6Li, 7Li, 10B and 11B at 9 angles from 200 to 1600 with time-of-flight techniques for a flight path of 3.6 m. The tritium gas cell used for the source introduced an energy spread of +- 35 keV. The detector was NE224 liquid scintillator of 5 cm thickness and 18 cm diameter housed in a large collimator-shield rotated on air pads. Multiple scattering corrections include energy-dependence of the differential cross sections of multiple events necessary for these very light nuclei. The coefficients B/sub L/ of Legendre polynomial expansions of the differential cross sections for 10B show broad resonance behavior near E/sub n/ approx. 4.2 MeV and 7.5 MeV. For the 30 energies at which angular distributions were measured on 10B the B/sub L/ for L greater than or equal to 5 were negligible. The strong resonance structure present in the B/sub L/ for 11B is much narrower and shows considerable interference effects between states. Contributions by resonant d-waves are large as would be expected in this energy region which contains the parents of the T = 1 analog states in 12C of the giant dipole resonance. Angular distributions for 11B were measured at 60 energies between 4 MeV and 8 MeV and again B/sub L/for L greater than or equal to 5 were negligible. From R-matrix analyses of the data, properties of these states will be extracted. This yields information on particle-hole structure of 12B expected in this region and affords a comparison with model calculations in the A = 12 system