National Research Centre "Kurchatov Institute" B. P. Konstantinov Petersburg Nuclear Physics Institute, Gatchina, Leningrad District 188300, Russia.
J Chem Phys. 2016 Dec 7;145(21):214301. doi: 10.1063/1.4968229.
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.
精确的理论研究对解释实验具有重要意义，这些实验旨在寻找基本相互作用的时间反转（T）和空间宇称（P）对称性的违反，违反的表现为电子电偶极矩 eEDM 和无量纲常数 k，这两个常数分别描述了 T，P-odd 赝标量-标量电子-核中性电流相互作用的强度。ACME 合作最近使用电子 HΔ 态的 ThO 分子束[J. Baron 等人，Science 343, 269 (2014)]改进了这些量的限制。我们应用联合直接相对论 4 分量和两步相对论赝势/恢复方法对 ThO 分子的Δ13 态的有效电场 E、T，P-odd 赝标量-标量相互作用的参数 W 和超精细结构常数进行基准计算。前两个参数是根据 eEDM 和 k 常数解释实验数据所必需的。我们同时对 ThO 的所有 98 个电子进行了电子相关的研究，计算水平达到了单、双和非迭代三振幅耦合簇（CCSD(T)）理论。还处理了价电子的迭代三振幅和非迭代四振幅对贡献。得到的数值为 E = 79.9 GV/cm，W = 113.1 kHz。这些值的理论不确定度估计比我们之前的研究小两倍左右[L. V. Skripnikov 和 A. V. Titov，J. Chem. Phys.，142, 024301 (2015)]。结果表明，内壳层和外壳层电子的相关性对有效电场的贡献为 9%。用相同的方法计算的Δ13 态的分子框架偶极矩和 ThO 的 HΔ→XΣ 跃迁能量与实验值非常吻合。
