Theoretical study of thorium monoxide for the electron electric dipole moment search, II: Electronic properties of $H^3\Delta_1$ in ThO

TL;DR

This paper provides improved theoretical calculations of key electronic properties of the ThO molecule's $H^3 riangle_1$ state, crucial for interpreting electron EDM experiments and reducing uncertainties in fundamental physics limits.

Contribution

It reports more accurate calculations of extit{E}$_{ ext{eff}}$, $W_{T,P}$, hyperfine constants, and the g-factor for ThO's $H^3 riangle_1$ state, including the first g-factor calculation, enhancing the reliability of EDM constraints.

Findings

extit{E}$_{ ext{eff}}$ = 81.5 GV/cm with 7 ext% uncertainty

$W_{T,P}$ = 112 kHz with 7 ext% uncertainty

First calculation of g-factor for the $H^3 riangle_1$ state

Abstract

Recently an improved limits on the electron electric dipole moment, \eEDM, and dimensionless constant, $k_{T,P}$, characterizing the strength of the T,P-odd pseudoscalar$-$scalar electron$-$nucleus neutral current interaction in the $H^3\Delta_1$ state of ThO molecule were obtained by ACME collaboration [Science 343, 269 (2014)]. The interpretation of the experiment in terms of fundamental quantities \eEDM\ and $k_{T,P}$ is based on the results of theoretical study of appropriate ThO characteristics, the effective electric field acting on electron, \Eeff, and a parameter of the T,P-odd pseudoscalar$-$scalar interaction, $W_{T,P}$, given in [J.Chem.Phys.\ 139, 221103 (2013)] by St.Petersburg group. To reduce the uncertainties of the given limits we report improved calculations of the molecular state$-$specific quantities \Eeff, 81.5~GV/cm, and $W_{T,P}$, 112~kHz, with the uncertainty within 7\% of the magnitudes. Thus, the values recommended to use for the upper limits of the quantities are 75.8~GV/cm and 104~kHz, correspondingly. The hyperfine structure constant, molecule-frame dipole moment of the $H^3\Delta_1$ state and $H^3\Delta_1\to X^1\Sigma^+$ transition energy which, in general, can serve as a measure of reliability of the obtained \Eeff\ and $W_{T,P}$ values are also calculated. Besides we report the first calculation of g-factor for the $H^3\Delta_1$ state of ThO. The results are compared to the earlier experimental and theoretical studies, and a detailed analysis of uncertainties of the calculations is given.