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Abstract. In a multidetector experiment on 26 or 30 AMeV 32S + 5SNi, up to four coincident heavier or intermediate-mass fragments were observed. One of these occasionally has the characteristics of a projectile-like fragment, up to three may be attributed to the decay of the heavy reaction product. Taking the velocity of the fragments as a measure of the heavy-product excitation energy, one finds evaporation, fission and multifragmentation to follow one another with rising excitation. Model simulations of sequential decay with up to two binary fissions and, alternatively, of simultaneous statistical multifragmentation were performed for comparison with experimental distributions of mass, velocity and (for events with three slow intermediate-mass fragments) relative azimuthal angle. Though in the three-fragment events indications of simultaneous multifragmentation are present, the sequential binary decay predominates. Evaporated protons and c~ particles detected in coincidence have a mean multiplicity growing with excitation energy, while the temperature governing the spectra has a plateau with a value of about 5.5 MeV.

Abstract.Correlations between two intermediate-mass fragments resulting from 840 MeV 32S projectiles interacting with 197Au were measured. The angular correlations and absolute two-fragment cross sections agree with predictions of a semi-microscopic model for direct dynamic projectile break-up. This suggests a predominantly direct mechanism for the production of intermediate-mass fragment pairs. It is argued that the intensity of such a channel which, compared to decays yielding particles, is much larger than observed for the sequential decay of corresponding primary excited nuclei, supports the direct-break-up interpretation. The model mechanism yields also strongly damped projectile fragments of intermediate mass.