John Kruse

Soft dipole resonance in exotic nuclei

Abstract Projectiles of 11 Li were photodisintegrated into 9 Li + n + n by absorption of a virtual photon in a Pb target. The momenta of the three particles in the final state were measured, and the dipole strength function was determined up to about 1 MeV above the disintegration threshold. On the average, the 9 Li residue had a greater velocity than the neutrons. Interpreted as a post-breakup acceleration of 9 Li in the coulomb field of the Pb nucleus, the lifetime of the excited 11 Li was found to be too short for the disintegration process to have gone through a resonant state such as the soft dipole resonance. Because the complete kinematics was measured, we could view the events in the rest frame of 11 Li. In that frame the distribution of angle between the two neutrons, when the response of the neutron detection system was taken account of, was isotropic. Hence, we have no evidence for a dineutron in 11 Li. Two recently-constucted neutron walls will be used in future experiments.

Final-state interactions in the system 8He+n

Final-state interactions in the systems 6He+n and 8He+n have been studied via the breakup of 30 MeV/u 10,11,12Be beams on a 9Be target. The results for the longitudinal and transverse momentum distributions of the outgoing neutron and fragment are presented and discussed.

New evidence for parity inversion in 10Li from 9Li and γ-ray coincidences

An experiment was performed at the National Superconducting Cyclotron Laboratory of Michigan State University to study the structure of neutron-unbound 10Li importantly associated to the understanding of the structure of two-neutron halo 11Li. The analysis of 9Li-γ coincidences from the single-proton stripping of 11Be demonstrates that the previously observed low decay energy virtual s-state in 10Li is a low-lying state which decays to the ground state of 9Li and therefore shows evidence for parity inversion in 10Li.