Theoretical study of thorium monoxide for the electron electric dipole moment search: Electronic properties of H3Δ1 in ThO

Recently, improved limits on the electron electric dipole moment, 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 the ACME collaboration [J. Baron et al., Science 343, 269 (2014)]. The interpretation of the experiment in terms of these fundamental quantities is based on the results of theoretical study of appropriate ThO characteristics, the effective electric field acting on electron, E-eff, and a parameter of the T, P-odd pseudoscalar-scalar interaction, W-T,W-P, given in Skripnikov et al. [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 E-eff, 81.5 GV/cm, and W-T,W-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 the H-3 Delta(1) -> X-1 Sigma(+) transition energy which, in general, can serve as a measure of reliability of the obtained E-eff and W-T,W-P values are also calculated. In addition, 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. (C) 2015 AIP Publishing LLC.