Impact-parameter dependence of giant resonance excitations in relativistic heavy-ion collisions

Angular distributions of Xe fragments produced in peripheral collisions of a 136 Xe beam ~700 MeV/nucleon! with 208 Pb and nat Sn targets were measured. Equivalent sharp-cutoff minimum impact parameters were derived on the basis of a semiclassical description for the electromagnetic excitation of one- and two-phonon giant resonances. The results are compared with current standard parametrizations of minimum impact parameters and with the soft-spheres model using realistic mass density distributions for projectile and targets. @S0556-2813~99!50611-0#