Elastodynamic Features of Nuclear Matter from Macroscopic Model of Giant Magnetic Resonances

Abstract

The collective model is presented providing a descriptive treatment of the magnetic resonant response of spherical nuclei. The model is based on macroscopic equations assuming elastodynamic behavior of the nuclear Fermi-continuum. Modelling a heavy nucleus by a spherical piece of an elastic continuous substance made up of a degenerate Fermi-system of nucleons, it is argued that nuclear resonant magnetization may be interpreted as the resultant of torsional wavelike vibrations excited inside a nuclear macroparticle. The emphasis is placed on the description of the giant magnetic dipole resonance. This resonance is associated with long wavelength vibrations of the magnetization current induced in the peripheral layer of finite depth, whereas the internal spherical region presumably unaffected by external perturbations is considered as an unperturbed core. The excited collective motion is found to behave like shear non-radial vibrations of a massive peripheral layer against a rotationally invariant core. The Extended Thomas-Fermi method is employed to generate a bulk density profile on the basis of Skyrme forces which is used as an input parameter in calculations of torsional inertia and stiffness of the collective Hamiltonian. Systematic calculations for the energy and total excitation probability of the giant M1 resonance are compared with data obtained both by nuclear resonance fluorescence measurements and by means of backward (e,e′) scattering.