Excited States of 11BE

The ¹¹B(⁷Li,⁷Be)¹¹Be reaction at 57 MeV incident energy was studied at forward angles in order to explore the ¹¹Be excitation energy spectrum. The ¹¹Be ground state and the states at E* = 0.32, 1.77, 2.67, 3.41, 3.89, 3.96, 6.05 MeV excitation energies were populated. The state at 6.05 MeV (FWHM 320 ± 20 keV) has not been previously observed. A structure at E* = 9.5 MeV and FWHM ≈ 9 MeV is observed which is compatible with the Spin Dipole Resonance (SDR) oscillation mode. The good energy resolution (~ 50 keV) allowed the identification of these transitions each for ⁷Be in its ground and first excited state at E* = 0.429 MeV. QRPA calculations reproduce ¹¹Be level structure below 2 MeV of excitation energy, while fail in describing the fragmentation of the strength above that energy.