A netron halo in 8He

The structure of $^8$He is investigated within a three-cluster microscopic model. The three-cluster configuration $\alpha+^2n+^2n$ was used to describe the properties of the ground state of the nucleus. The obtained results evidently indicate the existence of a neutron halo in $^8$He.Comment: 14 pages, 6 postscript figures, submitted to Phys. Atom. Nuc