Damping of the giant spin-flip dipole and spin-flip quadrupole charge exchange modes in 90Zr

The damping of the giant spin-flip dipole (L=1, S=1, T=1, Jπ=0-, 1-, 2-) and spin-flip quadrupole (L=2, S=1, T=1, Jπ=1+, 2+, 3+) charge exchange resonances in 90Zr is calculated in a microscopic nuclear structure model which includes both one-particle-one-hole (1p1h) and two-particle-two-hole (2p2h) configurations in a systematic way. It is shown that the coupling to 2p2h configurations gives rise to a strongly energy dependent spreading width which shifts a large fraction of transition strength to high excitation energies. The implications for the analysis of intermediate energy 90Zr(p,n) data is discussed. (orig.)