Spectroscopy ofHe7using theBe9(He6,Be8)transfer reaction

The unbound nucleus $^{7}\mathrm{He}$ has been investigated via the reaction of a 16.8 MeV $^{6}\mathrm{He}$ radioactive ion beam on a $^{9}\mathrm{Be}$ target. The measurement of the outgoing $^{8}\mathrm{Be}$ through its well characterized two-$\ensuremath{\alpha}$ decay permitted the energy of the $^{6}\mathrm{He}+n$ system to be reconstructed. Through comparison with a complete Monte Carlo simulation incorporating $R$-matrix lineshapes, the $^{7}\mathrm{He}$ ground state was determined to lie 0.380(28) MeV above the neutron decay with a width of $\mathrm{\ensuremath{\Gamma}}=0.179(21)$ MeV. A neutron spectroscopic factor $\text{SF}=0.608(18)$ was extracted in agreement with the most recent calculations. Significant evidence was found for a broad resonance lying at 2.6(2) MeV above threshold with a ${\mathrm{\ensuremath{\Gamma}}}_{\text{FWHM}}=2.3(3)$ MeV. These parameters are fully consistent with the properties of $1/{2}^{\ensuremath{-}}$ state reported by Wuosmaa et al. [Phys. Rev. C 72, 061301(R) (2005)]. Limits were also put on the presence of narrow resonances seen in earlier experiments.