Abstract
The heaviest bound isotope of boron has been investigated using exclusive measurements of its Coulomb dissociation, into and two neutrons, in collisions with Pb at . Enhanced electric dipole () strength is observed just above the two-neutron decay threshold with an integrated strength of for relative energies below 6 MeV. This feature, known as a soft excitation, provides the first firm evidence that has a prominent two-neutron halo. Three-body calculations that reproduce the energy spectrum indicate that the valence neutrons have a significant -wave configuration and exhibit a dineutronlike correlation.
- Received 9 March 2020
- Revised 24 April 2020
- Accepted 6 May 2020
DOI:https://doi.org/10.1103/PhysRevLett.124.212503
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