Rainer W. Hasse

Bio: Rainer W. Hasse is an academic researcher from Deutsche Forschungsgemeinschaft. The author has contributed to research in topics: Fission & Nucleon. The author has an hindex of 5, co-authored 7 publications receiving 144 citations.

Caloric curves and critical behavior in nuclei

Abstract: Data from a number of different experimental measurements are used to construct caloric curves for five different regions of nuclear mass. These curves are qualitatively similar, and exhibit plateaus at the higher excitation energies. The limiting temperatures represented by the plateaus decrease with increasing nuclear mass, and are in very good agreement with results of recent calculations employing either a chiral symmetry model or the Gogny interaction. This agreement strongly favors a soft equation of state. Evidence is presented which suggests that critical excitation energies and critical temperatures might be determined from caloric curve measurements when the mass variations inherent in such measurements are taken into account.

Density dependence of the symmetry energy and the nuclear equation of state: A dynamical and statistical model perspective

Abstract: The density dependence of the symmetry energy in the equation of state of isospin asymmetric nuclear matter is of significant importance for studying the structure of systems as diverse as the neutron-rich nuclei and the neutron stars. A number of reactions using the dynamical and the statistical models of multifragmentation, and the experimental isoscaling observable, are studied to extract information on the density dependence of the symmetry energy. It is observed that the dynamical and the statistical model calculations give consistent results assuming the sequential decay effect in dynamical model to be small. A comparison with several other independent studies is also made to obtain important constraints on the form of the density dependence of the symmetry energy. The comparison rules out an extremely ``stiff'' and ``soft'' forms of the density dependence of the symmetry energy with important implications for astrophysical and nuclear physics studies.

Single-Particle Motion in Nuclei

Abstract: The shell model and the optical model play a central role in the description of nuclear structure and of nuclear reactions. In both models, the average nucleon-nucleus interaction is described by a mean field. This field is complex in the case of the optical model and real in the case of the shell model. Here, we shall consider a unified treatment in which the shell-model potential is also complex and is the continuation of the optical-model potential. This will enable one to construct the complex shell-model potential by extrapolating the optical-model potential from positive toward negative energies. This extrapolation will be based on a dispersion relation that connects the real to the imaginary part of this unified mean field. This will also yield single-particle orbits, spectroscopic factors, distributions of single-particle strengths, and occupation probabilities. At the same time, we shall be led to a critical discussion of these concepts. They require due caution because, for instance, a mean field or a single-particle orbit are not true observables. It is the conjunction of many experimental data that shows that these quantities do have a physical meaning, i.e., that one should be able to define them in a way that is almost model independent. This will indeed turn out to be the case. Complications or refinements will be introduced in a gradual way.