Electron Electric Dipole Moment and Hyperfine Interaction Constants for ThO

Abstract

A recently implemented relativistic four-component configuration interaction approach to study ${\cal{P}}$- and ${\cal{T}}$-odd interaction constants in atoms and molecules is employed to determine the electron electric dipole moment effective electric field in the $\Omega=1$ first excited state of the ThO molecule. We obtain a value of $E_{\text{eff}} = 75.6 \left[\frac{\rm GV}{\rm cm}\right]$ with an estimated error bar of $3\%$ and $10\%$ smaller than a previously reported result [arXiv:1308.0414 [physics.atom-ph]]. Using the same wavefunction model we obtain an excitation energy of $T_v^{\Omega=1} = 5329$ [\cm], in accord with the experimental value within $2\%$. In addition, we report the implementation of the magnetic hyperfine interaction constant $A_{||}$ as an expectation value, resulting in $A_{||} = -1335$ [MHz] for the $\Omega=1$ state in ThO. The smaller effective electric field increases the previously measured upper bound to the electron electric dipole moment interaction constant [arXiv:1310.7534v2 [physics.atom-ph]] and thus mildly mitigates constraints to possible extensions of the Standard Model of particle physics.