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We present data on collective flow of neutrons in collisons of [sup 197]Au + [sup 197]Au at 400 MeV/nucleon. The azimuthal distribution about the beam axis is investigated with respect to the reaction plane as determined from light charged particles. The squeezeout'' of neutrons, perpendicular to the reaction plane, is observed for the first time. Quantitative agreement to a high level of accuracy is found between the behavior of neutrons and hydrogen ions.

The nuclear response of a medium-mass nucleus ([sup 136]Xe) to electromagnetic excitation in a near-relativistic heavy-ion collision was investigated in the reaction[sup 136]Xe(0.7[ital A] GeV)+Pb. From an exclusive measurement of the neutron decay of the excited [sup 136]Xe projectiles, strong excitations of giant resonances and, in particular, of the double isovector giant dipole resonance were identified. A resonance energy of 28.3[plus minus]0.7 MeV, a width of 6.3[plus minus]1.6 MeV, and a total cross section of 215[plus minus]50 mb were found for the double giant dipole resonance.

Cross sections for the two-body channels populated in the /sup 32/S+ /sup 24/Mg reaction at E/sub c.m./ = 60.8 MeV have been measured by use of a coincidence technique which allows correction for secondary light-particle evaporation. The data show reaction yields with full equilibration of energy and mass-asymmetry coordinates. These results suggest an asymmetric fission mechanism and are contrary to what is expected from the previously proposed ''orbiting'' mechanism in light systems.

Observation of asymmetric fission fragments from the fission of /sup 56/Ni as populated in the /sup 32/S + /sup 24/Mg reaction have been interpretted in the standard fission model. This analysis can be extended to even lighter systems which have asymmetric yields. (AIP)