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Proton-proton correlations at small relative momenta were measured for [sup 40]Ar+[sup 197]Au reactions at [ital E]/[ital A]=200 MeV. Comparing the correlation functions to predictions based on single-particle phase space distributions from microscopic Boltzmann-Uehling-Uhlenbeck and quantum-molecular-dynamics (QMD) simulations, no satisfactory agreement could be established. Calculations utilizing two-particle emission probabilities predicted by the QMD model differ significantly from the single-particle calculations and are much closer to the experimental observations at [ital E]/[ital A]=200 MeV, potentially signaling the importance of the two-particle density for the proton-proton correlation function.

The mean multiplicity of intermediate mass fragments (IMF) {l angle}{ital M}{sub IMF}{r angle} produced by fragmentation of Au projectiles interacting with targets of C, Al, Cu, and Pb at an incident energy of {ital E}/{ital A}=600 MeV is compared to predictions of statistical multifragmentation and sequential evaporation models. The initial conditions for the calculations were provided by Boltzmann-Uehling-Uhlenbeck simulations. In the high excitation energy regime where the IMF multiplicity reaches its maximum the observed universal correlation between {l angle}{ital M}{sub IMF}{r angle} and the total charge {ital Z}{sub bound} of projectile fragments with charges {ital Z}{ge}2 cannot be reproduced by a sequential evaporation code. In this regime the data are better described by statistical decay calculations which assume the formation of an expanded nuclear system and a rather fast breakup.

Apparent emission temperatures of 4 He and 5 Li fragments were deduced for the reaction 40 Ar+ 197 Au at E / A =200 MeV from the relative population of excited states. Compared to previous measurements at E / A =60 MeV, the average emission temperatures increases by less than 2 MeV to a value of about 6 MeV. QMD calculations indicate that the momentum distribution of the nucleons forming a fragment is determined at a point where the system is still close to normal nuclear density and that they do not reflect the local momentum distribution of the surrounding nucleons. The simulations suggest that the observed low emission temperatures are a consequence of the dynamics of the fragment formation process.

Inclusive cross sections of intermediate mass fragments from the reaction {sup 40}Ar+{sup 197}Au at {ital E}/{ital A}=30 and 220 MeV were measured with a low threshold and over a large range of angles. The integrated cross sections are about 2 b at both energies but the emission characteristics change considerably. The increased isotropy of the angular distributions and the strongly reduced Coulomb repulsion at the higher bombarding energy suggest that the emission process evolves towards fragmentation of excited spectator matter in central ion-ion collisions.

We have studied multi-fragment decays of Au projectiles after collisions with C, Al, Cu and Pb targets at a bombarding energy of 600 MeV/nucleon. We examine the correlations between the charges emitted in these reactions. These correlations are given as a function of the total charge in bound fragments, Z bound , at forward angles, which is a measure of the violence of the collision and can be related to the impact parameter. The charge distributions have been fitted by a power law and the extracted τ parameter exhibits a minimum as a function of Z bound . We observe a strong reduction in the maximum charge, Z max , of the event with decreasing Z bound . For those events where Z max is less than half Z bound , the relative sizes of the two largest charges within the event cover the full spectrum of possibilities. The charge-Dalitz plots indicate that the multi-fragmentation events are not an extension of symmetric fission reactions. The event-by-event charge moments are examined to measure the size of the charge fluctuations. All of the charge correlations are independent of the target when plotted as a function of Z bound . The results are compared to both nuclear statistical and percolation calculations. The model predictions differ from each other, establishing that the observables are sensitive to how the available phase space is populated. The sequential nuclear model predicts too asymmetric a decay, while the simultaneous model predicts too symmetric a break-up. The percolation model, which was adjusted to reproduce the size of Z max , correctly predicts the mean behaviour and the fluctuations of the lighter fragments.

We have studied multifragment decays of Au projectiles after collisions with C, Al, and Cu targets at a bombarding energy of 600 MeV nucleon. We find that with increasing violence of the collision, measured via the multiplicity of light particles, the mean multiplicity of intermediate-mass fragments originating from the projectile first increases to a maximum {l angle}{ital M}{sub IMF}{r angle}{congruent}3 and then decreases again. Calculations using the Boltzmann-Uehling-Uhlenbeck model suggest that the fragmentation is governed by the energy {ital E}{sub dep} deposited into the projectile spectator and that {l angle}{ital M}{sub IMF}{r angle} reaches its maximum around {ital E}{sub dep}{congruent}8 MeV/nucleon.

An electron scattering experiment on 110 Pd has been performed at fairly small momentum transfers q , searching for mixed symmetry J π = 1 + and 2 + states predicted by the interacting boson model (IBM). Only some rather weakly excited candidates have been found and used to derive limits for the transition strength of the mixed symmetry states. While the Ml strength is compatible with the IBM predictions there is less E2 strength than expected by the model.