Resonances in Small Fermi Systems

TL;DR

This paper investigates how the resonant response widths of small metal particles and nuclei depend on size, revealing systematic behaviors linked to quantum effects, shell structure, and thermal excitations, with a unified scaling approach.

Contribution

It provides a quantum model explaining the size dependence of resonance widths in metal particles and nuclei, and introduces a scaling method to compare these systems.

Findings

FWHM varies inversely with radius in metal particles and nuclei.

Shell structure causes oscillations in nuclear resonance widths.

Scaling by Fermi energies and wave vectors aligns metal and nuclear data.

Abstract

The systematics of the size dependence of the resonant response of small metal particles and nuclei to incident electromagnetic radiation is studied. The known radius$^{-1}$ variation of the full width at half maximum (FWHM) in matrix-embedded metal particles is qualitatively accounted for by a quantum calculation of the response within a simple model. In free clusters, the behaviour is more complicated, possibly because of thermal excitation of surface modes. For nuclei, the FWHM shows strong shell-structure-linked oscillations across the periodic table. Focussing on the lower envelope of the oscillations (magic nuclei), the downward trend of the FWHM is consistent with the radius$^{-1}$ variation. A schematic theoretical description of the systematics in nuclei is presented. If the FWHMs are scaled by the respective Fermi energies and the inverse radii by the Fermi wave vectors, the data sets for matrix-embedded metal particles and nuclei become comparable in magnitude.