Recently, improved limits on the electron electric dipole moment, and dimensionless constant, kT,P, characterizing the strength of the T,P-odd pseudoscalar-scalar electron-nucleus neutral current interaction in the H(3)Δ1 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, Eeff, and a parameter of the T,P-odd pseudoscalar-scalar interaction, WT,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 Eeff, 81.5 GV/cm, and WT,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)Δ1 state, and the H(3)Δ1 → X(1)Σ(+) transition energy which, in general, can serve as a measure of reliability of the obtained Eeff and WT,P values are also calculated. In addition, we report the first calculation of g-factor for the H(3)Δ1 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.

An experiment to search for the electron electric dipole moment (eEDM) on the metastable H 3 1 state of ThO molecule was proposed and now prepared by the ACME Collaboration [http://www.electronedm.org]. To interpret the experiment in terms of eEDM and dimensionless constant k T, P characterizing the strength of the T,P-odd pseudoscalar-scalar electron-nucleus neutral current interaction, an accurate theoretical study of an effective electric field on electron, E eff , and a parameter of the T,P-odd pseudoscalar-scalar interaction, W T ,P , in ThO is required. We report our results for E eff (84 GV/cm) and W T ,P (116 kHz) together with the hyperfine structure constant, molecule frame dipole moment, and H 3 1 → X 1 + transition energy, which can serve as a measure of reliability of the obtained E eff and W T ,P values. Besides, our results include a parity assignment and evaluation of the electric-field dependence for the magnetic g factors in the -doublets of H 3 1 .

A precise theoretical study of the electronic structure of heavy atom diatomic molecules is of key importance to interpret the experiments in the search for violation of time-reversal (T) and spatial-parity (P) symmetries of fundamental interactions in terms of the electron electric dipole moment, eEDM, and dimensionless constant, k, characterizing the strength of the T,P-odd pseudoscalar-scalar electron-nucleus neutral current interaction. The ACME collaboration has recently improved limits on these quantities using a beam of ThO molecules in the electronic HΔ state [J. Baron et al., Science 343, 269 (2014)]. We apply the combined direct relativistic 4-component and two-step relativistic pseudopotential/restoration approaches to a benchmark calculation of the effective electric field, E, parameter of the T,P-odd pseudoscalar-scalar interaction, W, and hyperfine structure constant in Δ13 state of the ThO molecule. The first two parameters are required to interpret the experimental data in terms of the eEDM and k constant. We have investigated the electron correlation for all of the 98 electrons of ThO simultaneously up to the level of the coupled cluster with single, double, and noniterative triple amplitudes, CCSD(T), theory. Contributions from iterative triple and noniterative quadruple cluster amplitudes for the valence electrons have been also treated. The obtained values are E = 79.9 GV/cm, W = 113.1 kHz. The theoretical uncertainty of these values is estimated to be about two times smaller than that of our previous study [L. V. Skripnikov and A. V. Titov, J. Chem. Phys., 142, 024301 (2015)]. It was found that the correlation of the inner- and outer-core electrons contributes 9% to the effective electric field. The values of the molecule frame dipole moment of the Δ13 state and the HΔ→XΣ transition energy of ThO calculated within the same methods are in a very good agreement with the experiment.

Relativistic ab initio calculations have been performed to assess the suitability of RaF for experimental search of P− and T,P−violating interactions. The parameters of P− and T,P−odd terms of the spin-rotational Hamiltonian have been calculated for the 2 Σ electronic ground state of 223 RaF molecule. They include the Wa parameter, which is critical in experimental search for nuclear anapole moment and the parameters W d and WSP required to obtain restrictions on the electric dipole moment of the electron and T,P−odd scalar−pseudoscalar interactions, respectively. The parameter X corresponding to the "volume effect" in the T,P−odd interaction of the 223 Ra nuclear Schiff moment with electronic shells of RaF has also been computed. Spectroscopic and hyperfine structure constants for 223 RaF and 223 Ra + have been computed as well, demonstrating the accuracy of the methods employed.

We report the results of a theoretical investigation of the electronic structure of the ThF+ cation, which is one of the most interesting systems to search for the electron electric dipole moment (eEDM) [Science 342, 1220[Science 342, (2013] and other effects of violation of time reversal (T) and spatial parity (P) symmetries in fundamental interactions. For the working 3A , state we find a quite high value of the effective electric field acting on unpaired electrons (37.3 GV/cm). The field will be required to interpret the experiment planned on ThF+ in terms of the eEDM. Within the concept of atoms in compounds [A. V. Titov, Y. V. Lomachuk, and L. V. Skripnikov, Phys. Rev. A 90, 052522 (2014)], we compare the ThF+ electronic structure with that of ThO. Also, we calculate other parameters of T,P-odd interactions: WT.P, which is needed for interpretation of the experiment in terms of the dimensionless constant kT P characterizing the strength of the 7\P-odd pseudoscalar-scalar electron-nucleus neutral current interaction (50 kHz); and WM, which is required to search for the 229Th nuclear magnetic quadrupole moment in 229ThF+ (0.88 1033 2 Z). A number of properties which can be measured are also calculated: the hyperfine structure constant, molecule-frame dipole moment, and g factor.

No abstract

Actinide compounds are very intriguing objects for the quantum chemistry because, on the one hand, these compounds are of great scientific and technological interest and, on the other hand, quantitative first principle based modeling of their electronic structure is extremely difficult because of strong relativistic effects and complicated electron correlation pattern. The efficiency of high-level all-electron relativistic methods in applications to complex actinide systems of practical interest is questionable and more economical but sufficiently accurate approaches to the studies of such systems are preferable. Recently, generalized relativistic effective core potentials (GRECPs) have been generated for actinides to perform accurate calculations of electronic structure and properties of their compounds with moderate computational cost. The accuracy of different GRECP versions is analyzed in atomic calculations and their applications to molecular and cluster calculations are reviewed. The results are compared with available experimental data and other theoretical studies.

No abstract