82 v 1 1 9 O ct 2 00 4 Self - consistent Green ’ s function calculations of 16 O at small missing energies

Calculations of the one-hole spectral function of 16 O for small missing energies are reviewed. The self-consistent Green's function approach is employed together with the Faddeev equations technique in order to study the coupling of both particle-particle and particle-hole phonons to the single-particle motion. The results indicate that the characteristics of hole fragmentation are related to the low-lying states of 16 O and an improvement of the description of this spectrum, beyond the random phase approximation, is required to understand the experimental strength distribution. A first calculation in this direction that accounts for two-phonon states is discussed. §