# Sensitivity of isotope shift to distribution of nuclear charge density

## TL;DR

This paper investigates how nuclear charge distribution, including deformation and central density reduction, affects the field isotope shift beyond traditional radius-based models, especially in superheavy nuclei.

## Contribution

It introduces corrections to the field isotope shift accounting for nuclear deformation and central density reduction, extending beyond standard radius-based descriptions.

## Key findings

- Nuclear deformation influences isotope shift measurements.
- Central density reduction impacts isotope shift in superheavy nuclei.
- Relativistic effects modify the interpretation of nuclear charge distribution effects.

## Abstract

It is usually assumed that the field isotope shift (FIS) is completely determined by the change of the averaged squared values of the nuclear charge radius $\langle r^2\rangle$. Relativistic corrections modify the expression for FIS, which is actually described by the change of $\langle r^{2 \gamma}\rangle$, where $\gamma=\sqrt{1 - Z^2 \alpha^2}$. In the present paper we consider corrections to FIS which are due to the nuclear deformation and due to the predicted reduced charge density in the middle of the superheavy nuclei produced by a very strong proton repulsion (hole in the nuclear centre). Specifically, we investigate effects which can not be completely reduced to the change of $\langle r^2 \rangle$ or $\langle r^{2 \gamma}\rangle$.