# Weak quadrupole moments

## TL;DR

This paper introduces the concept of the weak quadrupole moment in nuclei, linking it to neutron distribution and parity violation, and calculates its effects in various isotopes to aid experimental detection of neutron quadrupoles.

## Contribution

It defines the weak quadrupole moment related to neutron distribution and provides calculations for its magnitude in multiple isotopes, enabling new experimental approaches.

## Key findings

- Weak quadrupole moments are related to neutron quadrupole distributions.
- Calculations of weak quadrupole moments for various isotopes.
- Predicted Lorentz invariance violating energy shifts.

## Abstract

Collective effects in deformed atomic nuclei present possible avenues of study on the non-spherical distribution of neutrons and the violation of the local Lorentz invariance. We introduce the weak quadrupole moment of nuclei, related to the quadrupole distribution of the weak charge in the nucleus. The weak quadrupole moment produces tensor weak interaction between the nucleus and electrons and can be observed in atomic and molecular experiments measuring parity nonconservation. The dominating contribution to the weak quadrupole is given by the quadrupole moment of the neutron distribution, therefore, corresponding experiments should allow one to measure the neutron quadrupoles. Using the deformed oscillator model and the Schmidt model we calculate the quadrupole distributions of neutrons, $Q_{n}$, the weak quadrupole moments ,$Q_{W}^{(2)}$, and the Lorentz Innvariance violating energy shifts in $^{9}$Be, $^{21}$Ne , $^{27}$Al, $^{131}$Xe, $^{133}$Cs, $^{151}$Eu, $^{153}$Eu, $^{163}$Dy, $^{167}$Er, $^{173}$Yb, $^{177}$Hf, $^{179}$Hf, $^{181}$Ta, $^{201}$Hg and $^{229}$Th.