Near threshold three-body final states in ⁷Li+⁷Li reactions at E_lab=34 MeV

Reactions of ⁷Li+⁷Li at E_lab=34 MeV, which lead to charged particle decaying excited states of ¹⁰Be, have been studied by use of a detection system sensitive to decay energies of a few hundred keV. The α-particle branching fractions in ¹⁰Be^*⃗⁴He+⁶He have been measured for excited states at E_x=7.542 and ∼9.6 MeV. For the 7.542 MeV state an unusually large separation radius is required to explain the observed branching fraction of Γ_α/Γ=(3.5±1.2)×10^-3. This result is interpreted in terms of the energy level structure of ¹⁰Be as related to analogous states in ¹²C and to the recent molecular orbital calculations. A new J^π=0^- state is observed in the decay ¹⁰Be^*⃗⁷Li^*(0.478 MeV)+t.