M. Zielinska-Pfabe

Nucleon emission from the interface of two colliding heavy ions

Abstract Energy and angular distributions of nucleons emitted in the early stages of intermediate energy heavy ion reactions are calculated. It is assumed that these nucleons originate in a hot region which is created near the contact point of touching spheres. Since the emission occurs during the very early stages of the reaction this model is applicable for both fusion and strongly damped collisions. Contributions from central to peripheral collisions are included. The model has been used for the study of the reaction 197 Au + 16 O and the results compare well with experiment.

Role of Thermal Fluctuations in a Classical Dynamical Model for Fission

We present a dynamical model for the motion of the fissioning nucleus in the classically allowed region after penetrating the barrier up to the scission point. The thermal fluctuations associated with the shape degrees of freedom are incorporated. The model has been applied to determine the mass and kinetic energy distributions for the spontaneous fission of 252Cf.

The Role of Deformation, Thermal Fluctuations and Single Particle Transfer in Strongly Damped Collisions

A dynamical model for strongly damped collisions with the inclusion of deformation, single particle transfer and thermal fluctuations is presented. We show that all these aspects are essential to account for the experimental data.

Stability and temperature of a hot compressed zone in heavy-ion collisions☆

Abstract It is shown that for heavy-ion reactions over 30–50 MeV/ A a hot zone can disintegrate yielding a high nuclear multiplicity. The temperature of the hot zone is calculated within the liquid drop model, where the volume term is determined using mean field theory. The dependence of the nuclear surface tension on temperature and density is also evaluated.

Radiation of pions from an expanding fireball

Abstract Using arguments from statistical mechanics we derive expressions for the pion multiplicities and spectra in high energy heavy ion reactions. We show that pions emerge during the early stage of the hydrodynamical expansion and that their energy distributions reflect mainly the temperature of the surface.

Post-scission dynamics in fission

Abstract A dynamical model for fission from the classical turning point to scission and beyond is presented. We consider the fissioning nucleus as well as the fission fragments as incompressible irrotational deformable charged liquid drops. We focus on the post-scission time evolution of the neck, stretching of the fragments, kinetic energy and excitation energy.

The temperature dependence of nuclear transport coefficients

SummaryWe estimate the static thermal conductivity χ0 and shear viscosity η0 over a broad temperature range. We argue that the transport coefficients decrease considerably when nuclear matter undergoes a firstorder phase transition from a Fermi liquid to a Fermi gas. At lower temperatures corrections due to the finite size of the nuclei are mandatory for models including pair interactions. Brief comments on the onset of «hot spots» (localized excitations) in heavy-ion-induced reactions are also included.RiassuntoSi stima la conduttività termica statica χ0 e la viscosità di taglio η0 in un ampio intervallo di temperature. Si prova che i coefficienti di trasporto decrescono considerevolmente quando la materia nucleare subisce una fase di transizione del primo ordine da un liquido di Fermi a un gas di Fermi. A temperature più basse, le correzioni dovute alla dimensione finita dei nuclei sono obbligatorie per modelli che includono interazioni di coppia. Sono anche inclusi brevi commenti sulla comparsa di «hot spot» (eccitazioni localizzate) in reazioni indotte da ioni pesanti.РезюмеМы оцениваем статическую теплопроводность χ0 и сдвиговую вязкость η0 в широкой области температур. Мы доказазываем, что транспортные коэффициенты существенно уменьшаются, когда ядерное вещество претерпевает фазовый переход из ферми-жидкости в Ферми-газ. При ниеких температурах необходимо учитывать поправки, обусловленные конечным размером ядер, в моделях, включающих парные взаимодиствия. В работе также вкратце обсуждается появление «горячих точек» (локализованных возбуждений) в тяжелом ионе, образованном в результате реакции.

Dynamical model for neck formation in the entrance channel of a heavy ion collision

The formation of the neck in the entrance channel is studied using a classical dynamical model. The dependence of neck radius on bombarding energy, mass or charge and angular momentum is discussed.

Microscopic treatment of Pauli blocking in strongly damped collisions

SummaryMicroscopic features of Pauli blocking for the analysis of strongly damped collisions are incorporated by considering the effect of this blocking on the elementary process of random single-nucleon transfer. We discuss a dynamical model with the inclusion of collective degrees of freedom and thermal fluctuation in these degrees of freedom as well as Pauli blocked transfer. Comparing our calculated dσ/dEloss and dσ/dZ with experimental data we find that Pauli blocking is very significant.

Role of single particle transfer in heavy ion fusion

Abstract Fusion excitation functions in heavy ion collision have been calculated taking into account the effect of random transfer of single particles in a classical dynamical model. The model has been applied to fusion of 16O+27Al and 40Ar +109Ag. The transfer does not affect the low energy fusion excitation function but the effect of transfer is appreciable for high energies.