Nuclear polarization effects in atoms and ions

TL;DR

This paper investigates how nuclear polarization effects influence atomic energy levels in heavy atoms and ions, providing numerical calculations, fitting functions, and an effective potential to aid in precision measurements and searches for new physics.

Contribution

It introduces a detailed numerical analysis of nuclear polarization effects, develops fitting functions, and constructs an effective potential for use in atomic and molecular energy level calculations.

Findings

Electric dipole polarization is enhanced by giant dipole resonance.

Electric quadrupole polarization is significant due to electron-nucleus interactions.

Provides effective potentials for modeling nuclear polarization effects.

Abstract

In heavy atoms and ions, nuclear structure effects are significantly enhanced due to the overlap of the electron wave functions with the nucleus. This overlap rapidly increases with the nuclear charge $Z$. We study the energy level shifts induced by the electric dipole and electric quadrupole nuclear polarization effects in atoms and ions with $Z \geq 20$. The electric dipole polarization effect is enhanced by the nuclear giant dipole resonance. The electric quadrupole polarization effect is enhanced because the electrons in a heavy atom or ion move faster than the rotation of the deformed nucleus, thus experiencing significant corrections to the conventional approximation in which they `see' an averaged nuclear charge density. The electric nuclear polarization effects are computed numerically for $1s$, $2s$, $2p_{1/2}$ and high $ns$ electrons. The results are fitted with elementary functions of nuclear parameters (nuclear charge, mass number, nuclear radius and deformation). We construct an effective potential which models the energy level shifts due to nuclear polarization. This effective potential, when added to the nuclear Coulomb interaction, may be used to find energy level shifts in multi-electron ions, atoms and molecules. The fitting functions and effective potentials of the nuclear polarization effects are important for the studies of isotope shifts and nonlinearity in the King plot which are now used to search for new interactions and particles.