# {\it Ab initio} studies of electron correlation effects in the atomic parity violating amplitudes in Cs and Fr

## TL;DR

This paper uses relativistic coupled-cluster theory to analyze electron correlation effects on atomic parity violation amplitudes in cesium and francium, emphasizing the importance of including perturbed double excitations for accuracy.

## Contribution

It presents a comprehensive relativistic coupled-cluster calculation of parity violating amplitudes in Cs and Fr, highlighting the significance of perturbed double excitations.

## Key findings

- Perturbed doubly excited states significantly impact parity violation calculations.
- Relativistic coupled-cluster theory effectively captures correlation effects.
- Comparison of results enhances understanding of atomic parity violation in Cs and Fr.

## Abstract

We have studied the correlation effects in Cs and Fr arising from the interplay of the residual Coulomb interaction to all orders and the neutral weak interaction which gives rise to the parity violating electric dipole transition to first order, within the framework of the relativistic coupled-cluster theory which circumvents the constrain of explicitly summing over the intermediate states. We observe that, the contributions arising from the perturbed doubly excited states are quite significant and hence, any calculation should not be considered accurate unless it includes the perturbed double excitations comprehensively. In this article, we have reported a comparative study of various results related to the parity violation in Cs and Fr.