Isospin of intermediate mass fragments produced in peripheral, midperipheral, and central collisions from the [Formula Presented] reactions at [Formula Presented] MeV

Isotopic yields of IMF’s produced in the [Formula Presented] reactions at [Formula Presented] MeV are investigated. Analysis of experimental data from the CRL-Laval [Formula Presented] multidetector array focuses on events where at least [Formula Presented] of the charge and momentum were detected for the [Formula Presented] system. Averaged isospin ratios [Formula Presented] for IMF’s with [Formula Presented] and 4 are plotted as a function of emission angle and parallel velocity in the center-of-mass frame. Results from simulations with the statistical codes SMM and GEMINI, assuming an equilibrated source, are compared to the experimental ratios. The ratios seem to indicate the presence of a midrapidity necklike structure that would produce IMF’s richer in neutrons than the two main emitters, even for very central collisions.