Search

We present a four-component relativistic approach to describe the effects of the nuclear spin-dependent parity-violating (PV) weak nuclear forces on nuclear spin-rotation (NSR) tensors. The formalism is derived within the four-component polarization propagator theory based on the Dirac–Coulomb Hamiltonian. Such calculations are important for planning and interpretation of possible future experiments aimed at stringent tests of the standard model through the observation of PV effects in NSR spectroscopy. An exploratory application of this theory to the chiral molecules H2X2 (X = 17O, 33S, 77Se, 125Te, and 209Po) illustrates the dramatic effect of relativity on these contributions. In particular, spin-free and spin–orbit effects are even of opposite signs for some dihedral angles, and the latter fully dominate for the heavier nuclei. Relativistic four-component calculations of isotropic nuclear spin-rotation constants, including parity-violating electroweak interactions, give frequency differences of up to 4.2 mHz between the H2Po2 enantiomers; on the nonrelativistic level of theory, this energy difference is 0.1 mHz only. [ABSTRACT FROM AUTHOR]

Theoretical calculations based on the Diracâ€"Coulombâ€"Breit relativistic coupled cluster method have been carried out for the electron affinities and ionization potentials (IPs) of the superheavy element nihonium (Nh) and its lighter homologues In and Tl. The In and Tl calculations are in agreement with measurement within uncertainties. For Nh, where experiment is yet unknown, we predict the IP of 7.569(48) eV and electron affinity of 0.776(30) eV. [ABSTRACT FROM AUTHOR]

Theoretical investigation of atomic and chemical properties of the elements at the low edge of the periodic table, called transactinide or superheavy elements (SHEs), sheds light on the effects of relativity on their electronic structure, revealing significant modification of the known regularities of the Periodic Law. The experimental study of the SHEs is targeting mainly the development of extreme ("atom-at-a-time") chemistry and spectroscopy. The updated periodic table contains seven full periods with 118 elements, including 15 transactinides or super-heavy elements, from the lightest rutherfordium (Z = 104) to the heaviest, recently named oganesson (Z = 118). There have been attempts to synthesize the next transactinide elements with atomic numbers 119 and 120, starting the eighth period of the periodic table [1], but the very low cross-sections (below 0.4 pb) frustrated these efforts. In order to increase the production rate of the known SHE isotopes by one or two orders of magnitude, required for successful synthesis of new elements with Z > 118, a new and unique experimental complex, the SHE Factory, has recently been established in Dubna. This facility is expected to make substantial breakthroughs in the physical and chemical research of the heaviest nuclei and elements; the first experiments are already planned for 2019 [2]. [ABSTRACT FROM AUTHOR]

Mössbauer isomer shifts of129I and127I in the ICl, IBr and I2molecules are studied. Filatov's formulation is used, based on calculating the electronic energy change of the two systems involved in the Mössbauer ? transition, the source and absorber. The energy difference between the transitions in the two systems determines the shift. The effects of relativity and electron correlation on the shifts are investigated. The exact two-component (X2C) and the four-component relativistic schemes give virtually identical results; the non-relativistic approach yields about 50% of the relativistic shifts. Electron correlation is included by coupled-cluster singles-and-doubles with perturbative triples [CCSD(T)]; it reduces Hartree–Fock shifts by 15%–20%. Basis sets are increased until the isomer shifts converge. The final results, calculated with the converged basis in the framework of the X2C Hamiltonian and CCSD(T) correlation, give an agreement of 10% or better with experimental data. [ABSTRACT FROM AUTHOR]

Parity non-conservation (PNC) due to the weak interaction is predicted to give rise to enantiomer dependent vibrational constants in chiral molecules, but the phenomenon has so far eluded experimental observation. The enhanced sensitivity of molecules to physics beyond the Standard Model (BSM) has led to substantial advances in molecular precision spectroscopy, and these may be applied to PNC searches as well. Specifically, trapped molecular ion experiments leverage the universality of trapping charged particles to optimize the molecular ion species studied toward BSM searches, but in searches for PNC, only a few chiral molecular ion candidates have been proposed so far. Importantly, viable candidates need to be internally cold, and their internal state populations should be detectable with high quantum efficiency. To this end, we focus on molecular ions that can be created by near threshold resonant two-photon ionization and detected via state-selective photo-dissociation. Such candidates need to be stable in both charged and neutral chiral versions to be amenable to these methods. Here, we present a collection of suitable chiral molecular ion candidates we have found, including CHDBrI+ and CHCaBrI+, that fulfill these conditions according to our ab initio calculations. We find that organo-metallic species have low ionization energy as neutrals and relatively high dissociation thresholds. Finally, we compute the magnitude of the PNC values for vibrational transitions for some of these candidates. An experimental demonstration of state preparation and readout for these candidates will be an important milestone toward measuring PNC in chiral molecules for the first time. [ABSTRACT FROM AUTHOR]

Abstract: The static dipole polarizabilities of the group 13 elements Ga, In and Tl in the three substates are calculated by the Fock space coupled cluster method. The ground 2 P 1/2 states are also studied by the single reference coupled cluster approach, with triple excitations included perturbatively. Very large basis sets are employed and extended to convergence. The effects of different parameters in the calculation (2- vs.4-component Hamiltonian, basis sets, coupled cluster expansion) are explored. The effect of the Gaunt interaction, which approximates the lowest order relativistic correction to the two-electron interaction, is also studied. Error bounds are estimated at 3% for the ground states and 5% for the J =3/2 states. The final recommended values for the ground states are α(Ga)=51.1(1.5) a.u., α(In)=62.0(1.9) a.u., and α(Tl)=52.1(1.6) a.u. The last two are in agreement with the experimental α(In)=69(8) a.u. and α(Tl)=51(7) a.u., and have error bars 4 times smaller. No experimental value is available for Ga, and the present calculations provide the first error bars for this element. [Copyright &y& Elsevier]

The intermediate Hamiltonian state universal (Hilbert-space) coupled-cluster method is presented, using a formalism similar to that developed for the valence universal (Fock-space) approach. The method is expected to be applicable to many states not accessible by traditional multiroot multireference all-order size-extensive approaches. A pilot application to excited states of atomic beryllium shows good convergence and agreement with experiment and full CI values. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [ABSTRACT FROM AUTHOR]

Abstract: The electron affinity (EA) of element 114 is calculated by the mixed sector intermediate Hamiltonian coupled cluster method, using large basis sets and model spaces. Similar calculations reproduce the EA of the lighter homologues Sn and Pb within 5%. This good agreement lends credence to the result obtained for element 114, predicting that the superheavy element will have no electron affinity and will not bind an extra electron. Trends in group 14 and the relativistic destabilization of the E114 orbital support this conclusion. [Copyright &y& Elsevier]

The isotopically chiral molecular ion CHDBrI+ is identified as an exceptionally promising candidate for the detection of parity violation in vibrational transitions. The largest predicted parity-violating frequency shift reaches 1.8 Hz for the hydrogen wagging mode which has a sub-Hz natural line width and its vibrational frequency auspiciously lies in the available laser range. In stark contrast to this result, the parent neutral molecule is two orders of magnitude less sensitive to parity violation. The origin of this effect is analyzed and explained. Precision vibrational spectroscopy of CHDBrI+ is feasible as it is amenable to preparation at internally low temperatures and resistant to predissociation, promoting long interrogation times (Landau et al., J. Chem. Phys., 2023, 159, 114307). The intersection of these properties in this molecular ion places the first observation of parity violation in chiral molecules within reach. [ABSTRACT FROM AUTHOR]

A measurement of the magnitude of the electric dipole moment of the electron (eEDM) larger than that predicted by the Standard Model (SM) of particle physics is expected to have a huge impact on the search for physics beyond the SM. Polar diatomic molecules containing heavy elements experience enhanced sensitivity to parity (P) and time-reversal (T)-violating phenomena, such as the eEDM and the scalar–pseudoscalar (S–PS) interaction between the nucleons and the electrons, and are thus promising candidates for measurements. The NL-eEDM collaboration is preparing an experiment to measure the eEDM and S–PS interaction in a slow beam of cold BaF molecules [P. Aggarwal et al., Eur. Phys. J. D 72, 197 (2018)]. Accurate knowledge of the electronic structure parameters, Wd and Ws, connecting the eEDM and the S–PS interaction to the measurable energy shifts is crucial for the interpretation of these measurements. In this work, we use the finite field relativistic coupled cluster approach to calculate the Wd and Ws parameters in the ground state of the BaF molecule. Special attention was paid to providing a reliable theoretical uncertainty estimate based on investigations of the basis set, electron correlation, relativistic effects, and geometry. Our recommended values of the two parameters, including conservative uncertainty estimates, are 3.13 ± 0.12 × 1 0 24 Hz e cm for Wd and 8.29 ± 0.12 kHz for Ws. [ABSTRACT FROM AUTHOR]

We investigate the merits of a measurement of the permanent electric dipole moment of the electron (eEDM) with barium monofluoride molecules, thereby searching for phenomena of CP violation beyond those incorporated in the standard model (SM) of particle physics. Although the BaF molecule has a smaller enhancement factor in terms of the effective electric field than other molecules used in current studies (YbF, ThO and ThF+), we show that a competitive measurement is possible by combining Stark-deceleration, laser-cooling and an intense primary cold source of BaF molecules. With the long coherent interaction times obtainable in a cold beam of BaF, a sensitivity of 5 × 10−30 e⋅cm for an eEDM is feasible. We describe the rationale, the challenges and the experimental methods envisioned to achieve this target. [ABSTRACT FROM AUTHOR]

The NL-eEDM collaboration is building an experimental setup to search for the permanent electric dipole moment of the electron in a slow beam of cold barium fluoride molecules [NL-eEDM Collaboration, Eur. Phys. J. D 72, 197 (2018)]. Knowledge of the molecular properties of BaF is thus needed to plan the measurements and, in particular, to determine the optimal laser-cooling scheme. Accurate and reliable theoretical predictions of these properties require the incorporation of both high-order correlation and relativistic effects in the calculations. In this work, theoretical investigations of the ground and lowest excited states of BaF and its lighter homologs, CaF and SrF, are carried out in the framework of the relativistic Fock-space coupled cluster and multireference configuration interaction methods. Using the calculated molecular properties, we determine the Franck-Condon factors (FCFs) for the A 2 Π 1 / 2 → X 2 Σ 1 / 2 + transition, which was successfully used for cooling CaF and SrF and is now considered for BaF. For all three species, the FCFs are found to be highly diagonal. Calculations are also performed for the B 2 Σ 1 / 2 + → X 2 Σ 1 / 2 + transition recently exploited for laser-cooling of CaF; it is shown that this transition is not suitable for laser-cooling of BaF, due to the nondiagonal nature of the FCFs in this system. Special attention is given to the properties of the A′2Δ state, which in the case of BaF causes a leak channel, in contrast to CaF and SrF species where this state is energetically above the excited states used in laser-cooling. We also present the dipole moments of the ground and excited states of the three molecules and the transition dipole moments (TDMs) between the different states. Finally, using the calculated FCFs and TDMs, we determine that the A 2 Π 1 / 2 → X 2 Σ 1 / 2 + transition is suitable for transverse cooling in BaF. [ABSTRACT FROM AUTHOR]

Potential energy curves of the electronic ground states of the group 12 dimers Zn and Cd were computed at the CCSD(T) level of theory, including full triple corrections $$\Updelta$$T in the coupled-cluster procedure, and spin-orbit (SO) contributions from four-component coupled-cluster calculations, extrapolated to the complete basis set (CBS) limit. For Hg, the potential energy curve published recently (Pahl et al. in J Chem Phys 132:114301, ] is complemented in this work by non-relativistic calculations to quantify and discuss relativistic effects. We obtain very accurate fits of our CBS/CCSD(T) and CBS/CCSD(T)+ $$\Updelta$$T data points to an analytically simple and computationally efficient extended Lennard Jones form. For the CBS/CCSD(T)+ $$\Updelta$$T+SO curves, we obtain dissociation energies of D = 226 cm and D = 319 cm for Zn and Cd respectively, in very good agreement with recent theoretical calculations and experimental data. We also present equilibrium distances and rotational and vibrational spectroscopic constants to compare with available theoretical and experimental data. The results obtained for non-relativistically treated Hg continue nicely the trends with increasing atom number preset by Zn and Cd, confirming that indeed, relativistic effects account for the known peculiarities for the mercury dimer. [ABSTRACT FROM AUTHOR]

We report a methodology that allows the investigation of the consequences of the spin–orbit coupling by means of the QTAIM and ELF topological analyses performed on top of relativistic and multiconfigurational wave functions. In practice, it relies on the "state‐specific" natural orbitals (NOs; expressed in a Cartesian Gaussian‐type orbital basis) and their occupation numbers (ONs) for the quantum state of interest, arising from a spin–orbit configuration interaction calculation. The ground states of astatine diatomic molecules (AtX with X = AtF) and trihalide anions (IAtI−, BrAtBr−, and IAtBr−) are studied, at exact two‐component relativistic coupled cluster geometries, revealing unusual topological properties as well as a significant role of the spin–orbit coupling on these. In essence, the presented methodology can also be applied to the ground and/or excited states of any compound, with controlled validity up to including elements with active 5d, 6p, and/or 5f shells, and potential limitations starting with active 6d, 7p, and/or 6f shells bearing strong spin–orbit couplings. [ABSTRACT FROM AUTHOR]

Precise experimental setups for detection of variation of fundamental constants, scalar dark matter, or gravitational waves, such as laser interferometers, optical cavities, and resonant-mass detectors, are directly linked to measuring changes in material size. Here we present calculated and experiment-derived estimates for both α and μ dependence of lattice constants and bond lengths of selected solid-state materials and diatomic molecules that are needed for interpretation of such experiments. [ABSTRACT FROM AUTHOR]