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

A search for the J(pi) = 1/2(-) spin-orbit partner of the J(pi) = 3/2(-) ground state in He-7 has been performed with the Li-7(d, He-2) 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 Li-7 as well as on triton and He-4 clusters in the Li-7 ground state. A possible resonance at an excitation energy E-x approximate to 1.45 MeV with a width Gamma approximate to 2.0 MeV is suggested when the quasifree charge-exchange process on Li-7 is constrained by a measurement of the Li-6(d, He-2) reaction. Gamow-Teller strengths for transitions to the lowest states in He-7 deduced from the differential cross sections are in remarkable agreement with results from ab initio quantum Monte Carlo calculations. (c) 2006 Elsevier B.V. All rights reserved.