Participation in the S306 Experiment at GSI in January 2009

点击翻译按钮获取中文摘要

We propose to study the ground-state properties of neutron-rich nuclei 27,29Ne (N=17,19), 30Na,31Mg, 32Al (N=19), 33Mg, 34Al ( N=21)), investigating the shell structure of neutron-rich nuclei around N~20, through Coulomb break up of secondary beams at intermediate energy (400-500 MeV/A). This is a completely different method than those which have been used so far to study the ground-state properties of these nuclei. The secondary beams can be obtained by fragmentation of an 40Ar beam at an energy 550 MeV/nucleon delivered by the SIS facility at GSI, Darmstadt. The experiment will be performed at the FRS-LAND-ALADIN setup by detecting forward focussed neutrons of high energy ( 200-500 MeV), fragments (projectile like with energy 400-500 MeV/nucleon) and transition gamma-rays from excited fragments in coincidence with the corresponding projectile. The ground-state properties, i.e., ground state configuration, spin and hence occupation of valence neutron(s) can be obtained by comparing both cross section and shape of the experimental invariant mass analysis spectra with those calculated in a direct-breakup model. Information about the shell structure, particularly, the possibility of an inversion of nd3/2 - nf7/2 , p3/2,1/2 orbitals can be deduced.