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The azimuthal angle distributions of neutral pions at midrapidity from Au+Au reactions at 1 GeV/nucleon incident energy have been measured. An enhanced emission of [pi][sup 0]'s perpendicular to the reaction plane is observed. The azimuthal asymmetry is dependent on the [pi][sup 0] momentum: the [pi][sup 0] spectrum perpendicular to the reaction plane is harder than in the reaction plane. The strength of the observed asymmetry appears to be more pronounced for [pi][sup 0] than for charged particles and neutrons.

Isotopically resolved yields of complex particles and fragments from the reaction /sup 12/C on /sup 197/Au at three bombarding energies E/A = 30, 48, and 84 MeV were measured. Specific entropies S/A were derived from the isotope yield ratios using a quantum statistical model. The entropy increases with the bombarding energy in the case of preequilibrium light particles but, for intermediate mass fragments, has an energy-independent value of S/Aapprox. =2.3.

Correlations between intermediate-mass fragments (IMF's) and heavy fragments were measured for $^{18}\mathrm{O}$-induced reactions on $^{\mathrm{nat}}\mathrm{Ag}$ and $^{197}\mathrm{Au}$ at $\frac{E}{A}=84$ MeV. Correlations of two coincident IMF's show a depletion at small relative velocities ${v}_{\mathrm{rel}}\ensuremath{\le}1$ cm/ns, reflecting the proximity of the two IMF's at the point of creation. However, the time scales for IMF emission derived from this correlation are similar to those of binary-IMF-heavy-recoil coincidences which indicates a sequential nature of multifragment emission in these reactions.

Isotopically resolved yields of intermediate-mass fragments from $^{12}\mathrm{\ensuremath{-}}$ and $^{18}\mathrm{induced}$ reactions on $^{58}$,64Ni, $^{\mathrm{nat}}\mathrm{Ag}$, and $^{197}\mathrm{Au}$ at E/A=84 MeV were measured. The systematic variation of the yield ratios with projectile and target shows that these fragments are produced by a mechanism that involves the whole target nucleus. It is demonstrated that, within a statistical interpretation, the isotope-yield ratios are a measure of the entropy and determine a relation between temperature and density at breakup.