Hyeji Lee

• Lee, Hyeji (2026). Coulomb Dissociation of 17B. Full text in Research Archive Show summary

  The neutron halo is one of the most intriguing features in systems with a large excess of neutrons compared to protons, providing valuable information about weakly bound many-body systems near the neutron drip line. 17B has long been regarded as a two-neutron halo nucleus based on various experimental observations. However, recent studies suggest otherwise due to a dominant d-wave configuration of the valance neutrons and due to the presence of a thick neutron skin. In this work, we report the first measurement of electric dipole (E1) excitation of 17B. A kinematically complete measurement was performed at RIBF, RIKEN, using the SAMURAI spectrometer. A 17B beam at 270MeV/u was impinged on a Pb target causing Coulomb dissociation (CD), and the breakup fragments 15B and two neutrons were detected in coincidence. From this measurement, the differential CD cross section and the E1 strength distribution were extracted. The observed E1 strength distribution indicates that 17B has a weakly developed halo. These results provide important structural information on 17B and they contribute to setting the criteria required for neutron halo formation.

• Lee, Hyeji (2026). Coulomb Dissociation of 17B. Full text in Research Archive Show summary

  The neutron halo is one of the most intriguing features in systems with a large excess of neutrons compared to protons, providing valuable information about weakly bound many-body systems near the neutron drip line. 17B has long been regarded as a two-neutron halo nucleus based on various experimental observations. However, recent studies suggest otherwise due to a dominant d-wave configuration of the valance neutrons and due to the presence of a thick neutron skin. In this work, we report the first measurement of electric dipole (E1) excitation of 17B. A kinematically complete measurement was performed at RIBF, RIKEN, using the SAMURAI spectrometer. A 17B beam at 270MeV/u was impinged on a Pb target causing Coulomb dissociation (CD), and the breakup fragments 15B and two neutrons were detected in coincidence. From this measurement, the differential CD cross section and the E1 strength distribution were extracted. The observed E1 strength distribution indicates that 17B has a weakly developed halo. These results provide important structural information on 17B and they contribute to setting the criteria required for neutron halo formation.

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