MICROSCOPIC DESCRIPTION OF THE ALPHA+O-16 SYSTEM IN A MULTICLUSTER MODEL

The multicluster generator coordinate method is applied to a microscopic study of the Ne-20 spectroscopy and of the O-16(alpha, gamma)Ne-20 capture cross section. The O-16 nucleus is described by four alpha clusters located on the apexes of a tetrahedron. The good quantum numbers of the O-16 and alpha+O-16 wave functions are restored by a multiple angular-momentum projection. With respect to the usual two-center approach, where O-16 is described by a closed p shell, the five-alpha model improves different Ne-20 spectroscopic properties. The O-16(alpha, gamma)Ne-20 S factor is reduced by about 30% at astrophysical energies.