Three-body properties of low-lying 12Be resonances

摘要

We compute the three-body structure of the lowest resonances of 12Be considered as two neutrons around anninert 10Be core. This is an extension of the bound-state calculations of 12Be into the continuum spectrum. Weninvestigate the lowest resonances of angular momenta and parities, 0±, 1−, and 2+. Surprisingly enough, theynall are naturally occurring in the three-body model. We calculate bulk structure dominated by small-distancenproperties as well as decays determined by the asymptotic large-distance structure. Both 0+ and 2+ have two-bodyn10Be-neutron d-wave structure, while 1− has an even mixture of p and d waves. The corresponding relativenneutron-neutron partial waves are distributed among s, p, and d waves. The branching ratios show differentnmixtures of one-neutron emission, three-body direct, and sequential decays. We argue for spin and parities 0+,n1−, and 2+ for the resonances at 0.89, 2.03, and 5.13, respectively. The computed structures are in agreementnwith existing reaction measurements.