Density profiles and collective excitations of a trapped two component Fermi vapour

We discuss the ground state and the small-amplitude excitations of a degenerate vapour of fermionic atoms placed in two hyperfine states inside a spherical harmonic trap. An equations-of-motion approach is set up to discuss the hydrodynamic dissipation processes from the interactions between the two components of the fluid beyond mean-field theory and to emphasize analogies with spin dynamics and spin diffusion in a homogeneous Fermi liquid. The conditions for the establishment of a collisional regime via scattering against cold-atom impurities are analyzed. The equilibrium density profiles are then calculated for a two-component vapour of 40K atoms: they are little modified by the interactions for presently relevant values of the system parameters, but spatial separation of the two components will spontaneously arise as the number of atoms in the trap is increased. The eigenmodes of collective oscillation in both the total particle number density and the concentration density are evaluated analytically in the special case of a symmetric two-component vapour in the collisional regime. The dispersion relation of the surface modes for the total particle density reduces in this case to that of a one-component Fermi vapour, whereas the frequencies of all other modes are shifted by the interactions.Comment: 14 pages, 4 figure

Fusion and Binary-Decay Mechanisms in the 35^{35}Cl+24^{24}Mg System at E/A ≈\approx 8 MeV/Nucleon

Compound-nucleus fusion and binary-reaction mechanisms have been investigated for the $^{35}$Cl+$^{24}$Mg system at an incident beam energy of E$_{Lab}$= 282 MeV. Charge distributions, inclusive energy spectra, and angular distributions have been obtained for the evaporation residues and the binary fragments. Angle-integrated cross sections have been determined for evaporation residues from both the complete and incomplete fusion mechanisms. Energy spectra for binary fragment channels near to the entrance-channel mass partition are characterized by an inelastic contribution that is in addition to a fully energy damped component. The fully damped component which is observed in all the binary mass channels can be associated with decay times that are comparable to, or longer than the rotation period. The observed mass-dependent cross sections for the fully damped component are well reproduced by the fission transition-state model, suggesting a fusion followed by fission origin. The present data cannot, however, rule out the possibility that a long-lived orbiting mechanism accounts for part or all of this yield.Comment: 41 pages standard REVTeX file, 14 Figures available upon request -

Recent results from the 11B(n,a)8Li reaction

info:eu-repo/semantics/publishe

Fusion cross-section of the

The 7Li + 11B reaction has been investigated in the energy range 5.5 MeV < E lab < 19MeV, by detecting γ-ray resulting from the de-excitation of evaporation residues. Statistical compound-nucleus calculations have been performed in order to extract both the cross-sections of individual exit channels and the fusion cross-section of the system. The total angular momentum that the compoundn ucleus 18O can support has been deduced and is seen to exhibit saturation for a limiting value of 8.5ħ at the high-energy extreme. The results are discussed in terms of the entrance channel and statistical yrast line limitations

Ionization of clusters produced in a hollow-cathode source

Summarization: The competition between neutral, positive and negative metal clusters produced via hollow-cathode discharge, was found to depend on the speed of the pump used to evacuate the cluster source as well as on the distance separating the cathode from a grounded grid introduced into the source to intercept the plasma beam. On this evidence it is concluded that the competition between positive and negative cluster ionization depends on the time interval during which clusters and plasma coexist. For coexistence time intervals less than about 1 ms, the relative abundances remain constant and the ratio of negative to positive cluster intensities ranges between 1.6±0.3 for Cu and 2.6±0.3 for Fe. For longer times, the abundance of negative clusters increases and that of positive decreases to the point of complete extinction. In terms of the cluster ionization mechanisms involved, it is suggested that initially several ionizing mechanisms producing negative as well as positive clusters proceed with comparable rates. At later time intervals, however, electron attachment becomes the dominant, if not the exclusive, particle ionization process.Presented on: Vacuu