Resonance states of ⁵H and ⁵Be in a microscopic three-cluster model

Resonance states of ⁵H and ⁵Be have been studied using microscopic t+n+n and h+p+p three-cluster models, respectively. The resonance positions are localized by the three-body complex scaling method. An effective nucleon-nucleon interaction, which reproduces the α+N low energy phase shifts and the energies of the 0⁺ ground and 2⁺ first excited states of ⁶He with the three-cluster model, is used to calculate resonance states of ⁵H and ⁵Be. This model can reasonably reproduce the experimental t+n and h+p phase shifts at low energies. It gives a 1/2⁺ broad resonance as the ground state in ⁵H and ⁵Be and in addition it gives two excited resonance states of 3/2⁺ and 5/2⁺. The resonance parameters of the 1/2⁺ state of ⁵H in the present model are close to those deduced from their recent experimental data by Korsheninnikov et al. The same effective nucleon-nucleon interaction is used for a tentative investigation in order to explore the possibility of a tetra-neutron (⁴n) resonance by means of the n+n+n+n four-body complex scaling method on a restricted set of model configurations. Our model does not give any evidence for a tetraneutron resonance.