Electromagnetic dissociation and soft giant dipole resonance of the neutron-dripline nucleus 11Li

Abstract

The electromagnetic dissociation (EMD) cross sections of light neutron-dripline projectile 11Li have been inferred from the target dependence of the interaction cross section, σ 1, and the two-neutron-removal cross section, σ −2n, at an incident energy of 0.8 GeV/nucleon. The EMD cross sections of 11Li projectiles on a lead target were found to be quite large; σ I EMD ( 11 Li+ Pb)=1.72 ±0.65 b and σ −2 n EMD ( 11 Li+ Pb)=0.89 ±0.10 b , which are approximately 80 times larger than those of 12C projectiles after scaling the cross section by Z proj 2. The large EMD cross section is related to the possible existence of a soft mode of the giant dipole resonance at low excitation energy in the extremely neutron-rich nuclei.