Search for a low-energy resonance in 7He with the 7Li(d, 2He) reaction

A search for the Jπ=1/2− spin-orbit partner of the Jπ=3/2− ground state in 7He has been performed with the Li7(d,He2) charge-exchange reaction. The experimental results are incompatible with recent claims of such a state at very low excitation energy [M. Meister, et al., Phys. Rev. Lett. 88 (2002) 102501]. A decomposition of the spectrum is performed taking into account known resonances and quasifree charge-exchange reactions on 7Li as well as on triton and 4He clusters in the 7Li ground state. A possible resonance at an excitation energy Ex≈1.45MeV with a width Γ≈2.0MeV is suggested when the quasifree charge-exchange process on 7Li is constrained by a measurement of the Li6(d,He2) reaction. Gamow-Teller strengths for transitions to the lowest states in 7He deduced from the differential cross sections are in remarkable agreement with results from ab initio quantum Monte Carlo calculations.