Elasticity of nuclear medium as a principal macrodynamical promoter of electric dipole pygmy resonance

Abstract

Motivated by arguments of the nuclear core-layer model formulated in [S.I. Bastrukov, J.A. Maruhn, Z.Phys. A 335 (1990) 139], the macroscopic excitation mechanism of electric pygmy dipole resonance (PDR) is considered as owing its origin to perturbation-induced effective decomposition of nucleus into two spherical domains - undisturbed inner region treated as static core and dynamical layer undergoing elastic shear vibrations. The focus is placed on the imprinted in the core-layer model mechanism of emergence of the low-energy dipole electric resonant excitation as Goldstone soft mode of translation layer-against-core oscillations. To accentuate this attitude we regain the obtained in the above paper spectral equation for the frequency of spheroidal elastic vibrations trapped in the finite-depth layer, but by working from canonical equation of elastic dynamics of continuous medium. The obtained analytic equations for the frequency of dipole vibrational state in question and its excitation strength exhibit fundamental character of this soft dipole mode of nuclear resonant response.

Accepted in Phys.Lett.B

References in corpus (4)

• Exotic modes of excitation in atomic nuclei far from stability
• Concentration of electric dipole strength below the neutron separation energy in N = 82 nuclei
• Spheroidal and torsional modes of quasistatic shear oscillations in the solid globe models of nuclear physics and pulsar astrophysics
• Eigenfrequency of nodeless elastic vibrations locked in the crust of quaking neutron star

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• Torsional nodeless vibrations of quaking neutron star restored by combined forces of shear elastic and magnetic field stresses
• Alfven seismic vibrations of crustal solid-state plasma in quaking paramagnetic neutron star
• Possible existence of pygmy dipole resonance built on excited states in a neutron-rich ${}^{80}$Ge nucleus