Proton angular distributions from the Be⁹(t, p)Be¹¹ reaction measured at 14 MeV triton energy

Compilation of energy levels of A = 11 and 12 nuclei, with emphasis on material leading to information about the structure of the A = 11 and 12 systems.

A ¹⁰Be target has been prepared from neutron-irradiated beryllium by the AREMIS isotope separator. Angular distributions from the (d, p), (d, t), (p, ṕ) and (d, d) reactions on ¹⁰Be were obtained with this target. Protons leading to the ground state and first excited state of ¹¹Be at 12.0 MeV incident deuteron energy indicate spin and parity assignments of $\text{1}\text{2}{}^{\mathrm{+}}$ and $\text{1}\text{2}{}^{\mathrm{-}}$, respectively. At an incident deuteron energy of 15.0 MeV, tritons could be detected up to an excitation of 5.5 MeV in ⁹Be. No evidence was seen for an l = 1 transition to known states at less than 3.0 MeV excitation in ⁹Be other than that to the ground state. Spectroscopic factors for observed states in the (d, p) and (d, t) reactions were obtained in DWBA analyses with reasonable parameters. Elastic and inelastic scattering of protons on ¹⁰Be were observed at several incident energies from 12.0 MeV to 16.0 MeV. The elastic scattering was compared with optical-model calculations, and a B(E2) value for the 3.37 MeV (2⁺ → 0⁺) transition was obtained by comparison of measured inelastic angular distributions with DWBA predictions. Spectroscopic information concerning transitions within the 1p shell is in good agreement with the values obtained in the shell-model calculations of Cohen and Kurath.

The distribution of the single-neutron strength up to an excitation energy E_x = 7.0 MeV in ¹¹Be was investigated with the ¹⁰Be(d, p)¹¹Be reaction at E_d = 25 MeV. The $\text{1}\text{2}{}^{\mathrm{+}}\text{,}\text{g.s.}\text{,}\text{1}\text{2}{}^{\mathrm{-}}\text{, 0.320}\text{MeV and}\text{1.785}\text{MeV}$ states are found to be excited with significant strength. The angular distribution for the 1.785 MeV state is typified by an orbital angular momentum transfer l_n = 2. This together with other available data indicate that its spin is $\text{J}{}^{\mathrm{\pi }}\text{=}\text{(5}\text{2)}{}^{\mathrm{+}}$. The spectroscopic factors for these three states are compared to the shell-model calculations of Teeters and Kurath and of Cohen and Kurath.