Resonances ofHe7using the complex scaling method

Abstract

We study the resonance spectroscopy of $^{7}\mathrm{He}$ in the $^{4}\mathrm{He}$$+n+n+n$ cluster model, where the motion of valence neutrons is described in the cluster orbital shell model. Many-body resonances are treated on the correct boundary condition as the Gamow states in the complex scaling method. We obtain five resonances and investigate their properties from the configurations. In particular, the $1/{2}^{\ensuremath{-}}$ state is found in a low excitation energy of 1.1 MeV with a width of 2.2 MeV, whereas the experimental determination of the position of this state is not so clear. We also evaluate the spectroscopic factors of the $^{6}\mathrm{He}$-$n$ components in the obtained $^{7}\mathrm{He}$ resonances. The importance of the $^{6}\mathrm{He}$(${2}^{+}$) state is shown in several states of $^{7}\mathrm{He}$.