Communication: Theoretical study of HfF⁺ cation to search for the T,P-odd interactions

The combined all-electron and two-step approach is applied to calculate the molecular parameters which are required to interpret the ongoing experiment to search for the effects of manifestation of the T,P-odd fundamental interactions in the HfF⁺ cation by Loh et al. [Science 342, 1220 (2013)] and Ni et al. [J. Mol. Spectrosc. 300, 12 (2014)]. The effective electric field that is required to interpret the experiment in terms of the electron electric dipole moment is found to be 22.5 GV/cm. In the work of Pospelov and Ritz [Phys. Rev. D 89, 056006 (2014)], it was shown that another source of the T,P-odd interaction, the scalar-pseudoscalar nucleus-electron interaction with the dimensionless strength constant k_T,P can dominate over the direct contribution from the electron electric dipole moment within the standard model and some of its extensions. Therefore, for the comprehensive and correct interpretation of the HfF⁺ experiment, one should also know the molecular parameter W_T,P, the value of which is reported here to be 20.1 kHz.