Theoretical evidence for di-molecular rotational behaviour in the hypernuclei 8ΣLi and 8ΣBe

We have performed microscopic cluster studies of light Σ-hypernuclei based on effective nucleon-nucleon and two different sigma-nucleon interactions. Our calculation confirms a bound O+ state in Σ4He and Σ4H, but reveals no evidence for levels in other partial waves. We have investigated the Σ8Li and Σ8Be hypernuclei in a microscopic 3-cluster approach. For both hypernuclei, our calculation shows that the lowest levels in the partial waves J=0-4 are bound or quasibound states of collective nature and show a strong α+Σ4H and α+Σ4He clustering. These levels form a sequence of states which can be well interpreted as arising from a rotating α+Σ4H or α+Σ4He di-molecule. Our results are compared to those of similar studies for light Λ-hypernuclei which do not show evidence for this kind of collective degrees of freedom. (orig.)