# Theoretical study of HfF$^+$ cation to search for the T,P-odd interactions

## TL;DR

This paper provides theoretical calculations of molecular parameters for HfF$^+$ cation crucial for interpreting experiments searching for T,P-odd fundamental interactions, including electron EDM and scalar-pseudoscalar interactions.

## Contribution

The study introduces precise theoretical values for key molecular parameters, notably the effective electric field and $W_{T,P}$, essential for analyzing T,P-odd interaction experiments with HfF$^+$.

## Key findings

- Effective electric field: 22.5 GV/cm
- Molecular parameter $W_{T,P}$: 20.1 kHz
- Supports interpretation of T,P-odd interaction measurements

## Abstract

The combined all-electron and two-step approach is applied to calculate the molecular parameters which are required to interpret the ongoing experiment to search for the effects of manifestation of the T,P-odd fundamental interactions in the HfF$^+$ cation by Cornell/Ye group [Science 342, 1220 (2013); J. Mol. Spectrosc. 300, 12 (2014)]. The effective electric field that is required to interpret the experiment in terms of the electron electric dipole moment is found to be 22.5 GV/cm. In Ref. [Phys. Rev. D 89, 056006 (2014)] it was shown that another source of T,P-odd interaction, the scalar-pseudoscalar nucleus-electron interaction with the dimensionless strength constant $k_{T,P}$ can dominate over the direct contribution from the electron EDM within the standard model and some of its extensions. Therefore, for the comprehensive and correct interpretation of the HfF$^+$ experiment one should also know the molecular parameter $W_{T,P}$ the value of which is reported here to be 20.1 kHz.