Evidence of soft dipole resonance in Li 11 with isoscalar character

Abstract

The first conclusive evidence of a dipole resonance in Li11 having isoscalar character observed from inelastic scattering with a novel solid deuteron target is reported. The experiment was performed at the newly commissioned IRIS facility at TRIUMF. The results show a resonance peak at an excitation energy of 1.03±0.03MeV with a width of 0.51±0.11MeV (FWHM). The angular distribution is consistent with a dipole excitation in the distorted-wave Born approximation framework. The observed resonance energy together with shell model calculations show the first signature that the monopole tensor interaction is important in Li11. The first ab initio calculations in the coupled cluster framework are also presented.