Differential cross sections for elastic and inelastic scattering of neutrons from isotopically enriched ${\mathrm{B}}^{10}$ samples have been measured for incident neutron energies from 3.02 to 6.45 MeV in 250 keV increments and from 7.02 to 12.01 MeV in 500 keV increments. Inelastic angular distributions for scattering to the states in parentheses in ${\mathrm{B}}^{10}$ have been measured from the indicated energy up to 12.01 MeV: (0.718) from 3.02 MeV; (1.74) from 3.27 MeV; (2.15) from 3.77 MeV; (3.59) from 5.52 MeV; (4.77) from 7.02 MeV. The measurements at 3.02, 3.51, 4.02, and 4.51 MeV were done at nine laboratory angles from 20° to 158° in 17.5° increments with a sample that is isotopically 95.86% ${\mathrm{B}}^{10}$. All other distributions measured scattering at 11 laboratory angles from 18° to 158° in 15° increments from a sample that is isotopically 99.49% ${\mathrm{B}}^{10}$. A multiple scattering code provided a simulation of the experimental scattering process allowing accurate corrections to the small measured inelastic cross sections. An eight-channel, multilevel R-matrix analysis was performed on the data. Level energies, spins, and parities were deduced for twelve levels above 13 MeV excitation in ${\mathrm{B}}^{11}$. Only two definite and three tentative assignments for T=12 levels had been made previously above 13 MeV. The two definite levels were confirmed. Good agreement between the data and the R-matrix calculation in all analyzed channels was obtained for the proposed structure.

• Received 8 January 1990

DOI:https://doi.org/10.1103/PhysRevC.42.190