15 research outputs found
Small damping approach in Fermi-liquid theory
The validity of small damping approximation (SDA) for the quasi-classical
description of the averaged properties of nuclei at high temperatures is
studied within the framework of collisional kinetic theory. The isoscalar
collective quadrupole vibrations in hot nuclei are considered. We show that the
extension of the SDA, by accounting for the damping of the distribution
function in the collision integral reduces the rate of variation
with temperature of the Fermi surface distortion effects. The damping of the
in the collision integral increases significantly the collisional
width of the giant quadrupole resonance (GQR) for small enough values of the
relaxation time. The temperature dependence of the eigenenergy of the GQR
becomes much more weaker than in the corresponding SDA case.Comment: 11 pages, 3 figure
Splashing and evaporation of nucleons from excited nuclei
The energy spectrum and the emission rate of particles emitted from excited
nucleus due to both the evaporation and the splashing (emission from a cold
vibrating nucleus) are calculated. We show that the collective motion of the
nuclear Fermi liquid is accompanied by direct non-statistical emission of
nucleons via the dynamical distortion of the Fermi surface.Comment: Revtex file (12 pages) and 2 figures. Submitted to Nucl. Phys.
Nuclear Shape Fluctuations in Fermi-Liquid Drop Model
Within the nuclear Fermi-liquid drop model, quantum and thermal fluctuations
are considered by use of the Landau-Vlasov-Langevin equation. The spectral
correlation function of the nuclear surface fluctuations is evaluated in a
simple model of an incompressible and irrotational Fermi liquid. The dependence
of the spectral correlation function on the dynamical Fermi-surface distortion
is established. The temperature at which the eigenvibrations become overdamped
is calculated. It is shown that, for realistic values of the relaxation time
parameter and in the high temperature regime, there is a particular eigenmode
of the Fermi liquid drop where the restoring force is exclusively due to the
dynamical Fermi-surface distortion.Comment: 23 pages, revtex, file and 3 figures, accepted for publication in
Nuclear Physics
Strongly damped nuclear collisions: zero or first sound ?
The relaxation of the collective quadrupole motion in the initial stage of a
central heavy ion collision at beam energies AMeV is studied
within a microscopic kinetic transport model. The damping rate is shown to be a
non-monotonic function of E_{lab} for a given pair of colliding nuclei. This
fact is interpreted as a manifestation of the zero-to-first sound transition in
a finite nuclear system.Comment: 15 pages, 4 figure
Fission Hindrance in hot 216Th: Evaporation Residue Measurements
The fusion evaporation-residue cross section for 32S+184W has been measured
at beam energies of E_beam = 165, 174, 185, 196, 205, 215, 225, 236, 246,and
257 MeV using the ATLAS Fragment Mass Analyzer. The data are compared with
Statistical Model calculations and it is found that a nuclear dissipation
strength, which increases with excitation energy, is required to reproduce the
excitation function. A comparison with previously published data show that the
dissipation strength depends strongly on the shell structure of the nuclear
system.Comment: 15 pages 9 figure
Deducing the nuclear-matter incompressibilty coefficient from data on isoscalar compression modes
Accurate assessment of the value of the incompressibility coefficient, K, of symmetric nuclear matter, which is directly related to the curvature of the equation of state (EOS), is needed to extend our knowledge of the EOS in the vicinity of the saturation point. We review the current status of K as determined from experimental data on isoscalar giant monopole and dipole resonances (compression modes) in nuclei, by employing the microscopic theory based on the random-phase approximation (RPA)