A study of fragment production in peripheral nuclear collisions at Fermi energies with a transport model (Boltzmann-Nordheim-Vlasov, BNV) is presented. It is compared to an experiment for the reaction 18 O on 181 Ta at E/A = 35 MeV measured at very forward angles. The data are decomposed empirically into a two-component structure, one centered at beam velocity ("direct component") and one at lower velocities ("dissipative component"). It is seen that BNV calculations describe the general features of the dissipative component of the reaction. The direct component of experimental data is interpreted with the Goldhaber model, and the width parameter is extracted. We also include the deexcitation of the excited, primary projectile-like residues due to statistical decay to be able to compare the results of calculations more in detail with experiment. This secondary evaporation is important for both isotope and velocity distributions, but a more consistent estimate of the excitation energy of the residues has to be persued.

Оставшаяся диссипативная (глубоко-неупругая) компонента хорошо описыва-ется в рамках примененного нами подхода. Показано, что отношение сечений прямой и диссипативной компонент, определяющее асимметрию скоростных распределений, зависит от формы функции отклонения фрагментов относитель-но оси пучка.

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Heavy ion collisions in the Fermi energy regime may simultaneously show features of direct and dissipative processes. To investigate this behavior in detail, we study isotope and velocity distributions of projectile-like fragments in the reactions 18 O (35MeV/A) + 9 Be( 181 Ta) at forward angles. We decompose the experimental velocity distributions empirically into two contributions: a direct, 'breakup' component centered at beam velocity and a dissipative component at lower velocities leading to a tail of the velocity distributions. The direct component is interpreted in the Goldhaber model, and the widths of the velocity distributions are extracted. The dissipative component is then successfully described by transport calculations. The ratio of the yields of the direct and the dissipative contributions can be understood from the behavior of the deflection functions. The isotope distributions of the dissipative component agree qualitatively with the data, but the modification due to secondary deexcitation needs to be considered. We conclude, that such reactions are of interest to study the equilibration mechanism in heavy ion collisions

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