Soft electric dipole (E1) response of 11Li has been investigated by a kinematical complete measurement of the Coulomb breakup at about 70 MeV/nucleon. A two-wall neutron detector setup allowed us to employ a kinematical condition to exclude fully the cross talk events even for the low relative energies (Erel) down to 0 MeV, thereby enhancing the experimental sensitivities in this energy region. In the Erel spectrum, a strong peak corresponding to the soft E1 excitation has been observed at about Ex = 0.6 MeV with B (E1) = 1.42 (18) e2 fm2 (4.5(6) Weisskopf units) for 0 ≤ Erel ≤ 3 MeV. The spectral shape as well as its amplitude is in excellent agreement with a three-body model with strong neutron-neutron correlation in the halo. Such correlation is further supported by the E1 non-energy weighted cluster sum rule. © 2007 Elsevier B.V. All rights reserved.
Nakamura, T. (2007). Soft E1 excitation of neutron-halo nuclei. Nuclear Physics A, 788(1–4), 243–250. https://doi.org/10.1016/j.nuclphysa.2007.01.011