Halo-induced large enhancement of soft dipole excitation of 11Li observed via proton inelastic scattering

J. Tanaka*, R. Kanungo, M. Alcorta, N. Aoi, H. Bidaman, C. Burbadge, G. Christian, S. Cruz, B. Davids, A. Diaz Varela, J. Even, G. Hackman, M. N. Harakeh, J. Henderson, S. Ishimoto, S. Kaur, M. Keefe, R. Krücken, K. G. Leach, J. LighthallE. Padilla Rodal, J. S. Randhawa, P. Ruotsalainen, A. Sanetullaev, J. K. Smith, O. Workman, I. Tanihata

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


Proton inelastic scattering off a neutron halo nucleus, 11Li, has been studied in inverse kinematics at the IRIS facility at TRIUMF. The aim was to establish a soft dipole resonance and to obtain its dipole strength. Using a high quality 66 MeV 11Li beam, a strongly populated excited state in 11Li was observed at Ex=0.80±0.02 MeV with a width of Γ=1.15±0.06 MeV. A DWBA (distorted-wave Born approximation) analysis of the measured differential cross section with isoscalar macroscopic form factors leads us to conclude that this observed state is excited in an electric dipole (E1) transition. Under the assumption of isoscalar E1 transitions, the strength is evaluated to be extremely large amounting to 30∼296 Weisskopf units, exhausting 2.2%∼21% of the isoscalar E1 energy-weighted sum rule (EWSR) value. The large observed strength originates from the halo and is consistent with the simple di-neutron model of 11Li halo.

Original languageEnglish (US)
Pages (from-to)268-272
Number of pages5
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
StatePublished - Nov 10 2017
Externally publishedYes


  • Isoscalar E1
  • Li
  • Neutron halo
  • Proton inelastic scattering
  • Soft-dipole resonance

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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