Malaya K. Nayak

Electron electric dipole moment and hyperfine interaction constants for ThO

Abstract A recently implemented relativistic four-component configuration interaction approach to study P - and T -odd interaction constants in atoms and molecules is employed to determine the electron electric dipole moment effective electric field in the Ω = 1 first excited state of the ThO molecule. We obtain a value of E eff = 75.2 GV cm with an estimated error bar of 3% and 10% smaller than a previously reported result (Skripnikov et al., 2013). Using the same wavefunction model we obtain an excitation energy of T v Ω = 1 = 5410 ( cm - 1 ), in accord with the experimental value within 2%. In addition, we report the implementation of the magnetic hyperfine interaction constant A | | as an expectation value, resulting in A | | = - 1339 (MHz) for the Ω = 1 state in ThO. The smaller effective electric field increases the previously determined upper bound (Baron et al., 2014) on the electron electric dipole moment to | d e | 9.7 × 10 - 29 e xa0cm and thus mildly mitigates constraints to possible extensions of the Standard Model of particle physics.

Theoretical study on ThF+, a prospective system in search of time-reversal violation

The low-lying electronic states of ThF+, a possible candidate in the search for - and -violation, have been studied using high-level correlated relativistic ab initio multi-reference coupled-cluster and configuration interaction approaches. For the state component with Ω = 1 (electron electric dipole moment ‘science state’) we obtain an effective electric field of , a - and -odd electron–nucleon interaction constant of kHz, a magnetic hyperfine interaction constant of MHz for 229Th (), and a very large molecular dipole moment of 4.03 D. The Ω = 1 state is found to be more than 300 cm−1 lower in energy than (), challenging the state assignment from an earlier theoretical study on this species (Barker et al 2012 J. Chem. Phys. 136 104305).

Search for parity and time reversal violating effects in HgH: Relativistic coupled-cluster study.

The high effective electric field (Eeff) experienced by the unpaired electron in an atom or a molecule is one of the key ingredients in the success of electron electric dipole moment (eEDM) experiment and its precise calculation requires a very accurate theory. We, therefore, employed the Z-vector method in the relativistic coupled-cluster framework and found that HgH has a very large Eeff value (123.2 GV/cm) which makes it a potential candidate for the next generation eEDM experiment. Our study also reveals that it has a large scalar-pseudoscalar (S-PS) P,T-violating interaction constant, Ws = 284.2 kHz. To judge the accuracy of the obtained results, we have calculated parallel and perpendicular magnetic hyperfine structure (HFS) constants and compared with the available experimental values. The results of our calculation are found to be in nice agreement with the experimental values. Therefore, by looking at the HFS results, we can say that both Eeff and Ws values are also very accurate. Further, We have derived the relationship between these quantities and the ratio which will help to get model independent value of eEDM and S-PS interaction constant.

Implementation of theZ-vector method in the relativistic-coupled-cluster framework to calculate first-order energy derivatives: Application to the SrF molecule

The molecular dipole moment and magnetic hyperfine structure constant demand an accurate wavefunction far from the nucleus and in near nuclear region, respectively. We, therefore, employ the so-called Z-vector method in the domain of relativistic coupled cluster theory to calculate the first order property of molecular systems in their open-shell ground state configuration. The implemented method is applied to calculate molecular dipole moment and parallel component of the magnetic hyperfine structure constant of SrF molecule. The results of our calculation are compared with the experimental and other available theoretically calculated values. We are successful in achieving good accordance with the experimental results. The result of our calculation of molecular dipole moment is in the accuracy of ~? 0.5 %, which is clearly an improvement over the previous calculation based on the expectation value method in the four component coupled cluster framework [V. S. Prasannaa et al, Phys. Rev. A 90, 052507 (2014)] and it is the best calculated value till date. Thus, it can be inferred that the Z vector method can provide an accurate wavefunction in both near and far nuclear region, which is evident from our calculated results.

TaN, a molecular system for probing

All-electron configuration interaction theory in the framework of the Dirac-Coulomb Hamiltonian has been applied to the TaN molecule, a promising candidate in the search for Beyond-Standard-Model physics in both the hadron and the lepton sector of matter. We obtain in the first excited {

{\cal{P,T}}

^3Delta_1

-violating hadron physics

} state a

Relativistic equation-of-motion coupled-cluster method using open-shell reference wavefunction: Application to ionization potential.

{cal{P,T}}

Relativistic equation-of-motion coupled-cluster method for the electron attachment problem

-odd effective electric field of

Calculation of P,T-odd interaction constant of PbF using Z-vector method in the relativistic coupled-cluster framework

36.0 left[frac{rm GV}{rm cm}right]