arXiv subjects

A. V. Titov

Publications and source records attributed to A. V. Titov.

At least 55 records · Page 3Linked to original sources

arXiv2013

Theoretical study of ThO for the electron electric dipole moment search

An experiment to search for the electron electric dipole moment (\eEDM) on the metastable $H^3Δ_1$ state of ThO molecule was proposed and now in the final stage of preparation 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 scalar T,P-odd electron-nucleus neutral current interaction, an accurate theoretical study of effective electric field on electron, Eeff, and $W_{T,P}$ constants is required. We report calculation of \Eeff\ (84 GV/cm) and a parameter of T,P-odd scalar neutral currents interaction, $W_{T,P}$ (116 kHz), together with the hyperfine structure constant, molecule frame dipole moment and $H^3Δ_1\to X^1Σ^+$ transition energy, which can serve as a measure of reliability of the obtained \Eeff\ and $W_{T,P}$ values. Besides, our results include a parity assignment and evaluation of the electric-field dependence for the magnetic $g$ factors for the $Ω$-doublets of $H^3Δ_1$.

physics.chem-ph↗

arXiv2013

Theoretical study of the parity and time reversal violating interaction in solids

A new theoretical approach to study the properties in solids, which are sensitive to a change of densities of the valence electrons in atomic cores (hyperfine structure constants, parameters of space parity (P) and time reversal (T) violation interaction, etc.) is proposed and implemented. It uses the two-step concept of calculation of such properties which was implemented earlier for the case of molecules [Progr.\ Theor.\ Chem.\ Phys. B 15, 253 (2006)]. The approach is applied to evaluate the parameter $X$ describing electronic density gradient on the Pb nucleus that is required to interpret the proposed experiment on PbTiO$_3$ crystal [PRA, 72, 034501 (2005)] to search for the Schiff moment of the $^{207}$Pb nucleus because of its high sensitivity to the corresponding P,T-violating interactions. For comparison the $X$ parameter has also been calculated on the Pb nucleus for the $^1Σ^+$ state of $^{207}$PbO molecule using the same density functionals as those utilized in PbTiO$_3$ studies. The relativistic coupled-clusters approach with single, double and perturbative triple cluster amplitudes, applicable to a few atom systems and providing high accuracy for $X$, is also applied to the PbO case to estimate the accuracy of density functional studies.

physics.chem-ph↗

arXiv2013

Centrifugal correction to hyperfine structure constants in the ground state of lead monofluoride, PbF

The sensitivity of the PbF molecule to the electron electric dipole moment has motivated detailed microwave spectroscopy. Previous theoretical approaches cannot fully explain the spectra. In turn, the explanation from "first principles" is very important both for molecular theory and for confirmation of the correctness of the interpretation of experimental data obtained with high precision. All of these issues are decisively addressed here. We have determined centrifugal correction parameters for hyperfine structure constants, both on lead and fluorine nuclei, of the $X^2Π_{1/2}$ state of lead monofluoride. These parameters were obtained by fitting experimentally observed pure rotational transitions and from {\it ab initio} calculations. We show that taking this correction into account is required to reproduce the experimental transition energies obtained in [Phys. Rev. A 84, 022508 (2011)].

physics.atom-ph↗

arXiv2012

The generalized relativistic effective core potential calculations of the adiabatic potential curve and spectroscopic constants for the ground electronic state of the Ca2

The potential curve, dissociation energy, equilibrium internuclear distance, and spectroscopic constants for the ground state of the Ca2 molecule are calculated with the help of the generalized relativistic effective core potential method which allows one to exclude the inner core electrons from the calculations and to take the relativistic effects into account effectively. Extensive generalized correlation basis sets were constructed and employed. The scalar relativistic coupled cluster method with corrections for high-order cluster amplitudes is used for the correlation treatment. The obtained results are analyzed and compared with the experimental data and corresponding all-electron results.

physics.chem-ph↗

arXiv2012

Optical Spectroscopy of Tungsten Carbide for Uncertainty Analysis in Electron Electric Dipole Moment Search

We perform laser induced fluorescence(LIF) spectroscopy on a pulsed supersonic beam of tungsten carbide(WC) molecules, which has been proposed as a candidate molecular system for a permanent Electric Dipole Moment(EDM) search of the electron in its rovibrational ground state of the X3Delta1 state. In particular, [20.6]Omega=2, v'=4 <- X3Delta1,v"=0 transition at 485nm was used for the detection. The hyperfine structure and the Omega-doublet of the transition are measured, which are essential for estimating the size of the potential systematic uncertainties for electron EDM measurement. For further suppression of the systematic uncertainty, an alternative electron EDM measurement scheme utilizing the g factor crossing point of the Omega-doublet levels is discussed. On the other hand, flux and internal temperature of the molecular beam are characterized, which sets the limit on the statistical uncertainty of the electron EDM experiment. With the given results, the prospect of electron EDM experiment with the X3Delta1 state of WC molecule is discussed.

physics.atom-ph↗

arXiv2012

Relativistic coupled cluster calculations of spectroscopic and chemical properties for element 120

The coupled cluster calculations with accounting for relativistic effects to study spectroscopic and chemical properties of element 120 (E120) are performed. Similar calculations for Ba are also done and they are in a good agreement with the experimental data. Dissociation energies of diatomic X-H and X-Au molecules, where X=E120, Ba, are calculated; for E120 they are found to be $1.5\div2$ times smaller than those for Ba.

physics.chem-ph↗

arXiv2010

Correlations beyond CCSD(T) for accurate study of Hg$_2$ and Cp$_2$

Contributions from high-order (non-perturbative triple and quadruple) cluster amplitudes to the dissociation energies, equilibrium distances, and vibrational constants for the ground states of van der Waals dimers Hg$_2$ and Cn$_2$ are evaluated. The incorporation of these contributions into the results of large-scale CCSD(T) calculations leads to non-negligible corrections of the computed molecular constants for Hg$_2$ (6% for the dissociation energy), and enables one to attain perfect agreement with the experimental values.

physics.chem-ph↗

arXiv2010

Towards the electron EDM search. Theoretical study of PbF

We report ab initio relativistic correlation calculations of potential curves and spectroscopic constants for four lowest-lying electronic states of the lead monofluoride. We also calculated parameters of the spin-rotational Hamiltonian for the ground and the first excited states including P,T-odd and P-odd terms. In particular, we have obtained hyperfine constants of the $^{207}$Pb nucleus. For the $^2Π_{1/2}$ state $A_\perp=-6859.6$ MHz, $A_\|=9726.9$ MHz and for the A$^2Σ^+_{1/2}$ $A_\perp=1720.8$ MHz, $A_\|=3073.3$ MHz. Our values of the ground state hyperfine constants are in good agreement with the previous theoretical studies. We discuss and explain seeming disagreement in the sign of the constant $A_\perp$ with the recent experimental data. The effective electric field on the electron $E_{eff}$, which is important for the planned experiment to search for the electric dipole moment of the electron, is found to be 3.3 * 10^{10} V/cm.

physics.atom-ph↗

arXiv2009

Accurate calculations of the dissociation energy, equilibrium distance and spectroscopic constants for the Yb dimer

The dissociation energy, equilibrium distance, and spectroscopic constants for the $^1Σ_g^+$ ground state of the Yb$_2$ molecule are calculated. The relativistic effects are introduced through generalized relativistic effective core potentials with very high precision. The scalar relativistic coupled cluster method particularly well suited for closed-shell van-der-Waals systems is used for the correlation treatment. Extensive generalized correlation basis sets were constructed and employed. The relatively small corrections for high-order cluster amplitudes and spin-orbit interactions are taken into account using smaller basis sets and the spin-orbit density functional theory.

physics.chem-ph↗

arXiv2008

Theoretical study of HfF$^+$ for the electron EDM search

We report ab initio relativistic correlation calculations of potential curves and electric dipole transition moments for ten low-lying electronic states, effective electric field on the electron, hyperfine constants and radiative lifetimes for the $^3Δ_1$ state of cation of the heavy transition metal fluoride HfF$^+$, which it is suggested to be used in experiments to search for the electric dipole moment of the electron. It is obtained that HfF$^+$ has deeply bound $^1Σ^+$ ground state; its dissociation energy is $D_e=6.4$ eV. The $^3Δ_1$ state is obtained as the relatively long-lived, with lifetime equal to about 0.4 s.,first excited state lying about 0.2 eV higher. The calculated effective electric field, $E_{eff}=W_d|Ω|$, acting on an electron in this state is $5.84*10^{24} Hz/{e*cm}$. The obtained hyperfine constants are $A_{\parallel}= -1239$ MHz for the $^{177}$Hf nucleus and $A_{\parallel}= -58.1$ MHz for the $^{19}$F nucleus.

physics.atom-ph↗

arXiv2007

Towards the electron EDM search: Theoretical study of HfF+

We report first ab initio relativistic correlation calculations of potential curves for ten low-lying electronic states, effective electric field on the electron and hyperfine constants for the ^3Δ_1 state of cation of a heavy transition metal fluoride, HfF^+, that is suggested to be used as the working state in experiments to search for the electric dipole moment of the electron. It is shown that HfF^+ has deeply bound ^1Σ^+ ground state, its dissociation energy is D_e=6.4 eV. The ^3Δ_1 state is obtained to be the relatively long-lived first excited state lying about 0.2 eV higher. The calculated effective electric field E_eff=W_d|Ω| acting on an electron in this state is 5.84*10^{24}Hz/(e*cm)

physics.atom-ph↗

arXiv2006

On search for nuclear Schiff moment in liquid xenon

A parameter of the P,T-odd Hamiltonian characterizing interaction of the nuclear Schiff moment with the gradient of electronic density on the Xe nucleus is calculated for an isolated Xe atom and for liquid xenon. We use more realistic model of liquid medium than the spherical cell model used in [B.Ravaine and A.Derevianko Phys. Rev. A, 69, 050101(R)(2004)]. Qualitatively different results for enhancement of the P,T-odd effect in liquid xenon are obtained when polarization of the medium is taken into account. Thus, proper choice of the liquid phase model is crucially important even for calculation of the properties dependent mostly on the electronic density near a nucleus.

physics.chem-ph↗

arXiv2006

Is E112 a relatively inert element? Benchmark relativistic correlation study of spectroscopic constants in E112H and its cation

We report the first results of relativistic correlation calculation of the spectroscopic properties for the ground state of E112H and its cation in which spin-orbit interaction is taken into account non-perturbatively. Studying the properties of E112 (eka-Hg) is required for chemical identification of its long-lived isotope, $^{283}$112. It is shown that appropriate accounting for spin-orbit effects leads to dramatic impact on the properties of E112H whereas they are not so important for E112H$^+$. The calculated equilibrium distance, $R_e^{calc}=1.662$ A, in E112H is notably smaller than $R_e^{expt}=(1.738\pm0.003)$ A and $R_e^{calc}=1.738$ A in HgH, whereas the dissociation energy, $D_e^{calc}=0.42$ eV, in E112H is close to $D_e^{expt}=0.46$ eV and $D_e^{calc}=0.41$ eV in HgH. These data are quite different from $R_e^{NH}=1.829$ A and $D_e^{NH}=0.06$ eV obtained for E112H within the scalar-relativistic Douglas-Kroll approximation [Nakajima and Hirao, Chem. Phys. Lett., 329, 511 (2000)]. Our results indicate that E112 should not be expected to be "more inert" than Hg in opposite to the results by other authors.

physics.chem-ph↗

arXiv2005

In search of the electron electric dipole moment: relativistic correlation calculations of the P,T-violation effect in the ground state of HI$^+$

We report the first results of ab initio relativistic correlation calculation of the effective electric field on the electron, E_eff, in the ground state of the HI$^+$ cation. This value is required for interpretation of the suggested experiment on search for the electron electric dipole moment. The generalized relativistic effective core potential, Fock-space relativistic coupled cluster with single and double cluster amplitudes and spin-orbit direct configuration interaction methods are used, followed by nonvariational one-center restoration of the four-component wavefunction in the iodine core. The calculated value of E_eff by the coupled cluster method is E_eff=0.345\times 10^{24}Hz/e*cm. Configuration interaction study gives E_eff=0.336\times 10^{24}Hz/e*cm (our final value). The structure of chemical bonding and contributions to E_eff in HI$^+$ is clarified and significant deviation of our value from that obtained in Ravaine etal Phys.Rev.Lett., 94, 013001 (2005) is explained.

physics.atom-ph↗

arXiv2005

Configuration interaction calculation of hyperfine and P,T-odd constants on ^{207}PbO excited states for the electron EDM experiments

We report first configuration interaction calculations of hyperfine constants A_\parallel and the effective electric field W_d acting on the electric dipole moment of the electron, in two excited electronic states of ^{207}PbO. The obtained hyperfine constants, A_\parallel = -3826 MHz for the a(1) state and A_\parallel = 4887 MHz for the B(1) state, are in very good agreement with the experimental data, -4113 MHz and 5000 \pm 200 MHz, respectively. We find W_d = -(6.1 ^{+1.8}_{-0.6}) 10^{24} Hz/(e cm) for a(1), and W_d = (8.0 \pm 1.6) 10^{24} Hz/(e cm) for B(1). The obtained values are analyzed and compared to recent relativistic coupled cluster results and a semiempirical estimate of W_d for the a(1) state.

physics.atom-ph↗

arXiv2005

Accounting for correlations with core electrons by means of the generalized relativistic effective core potentials: Atoms Hg and Pb and their compounds

A way to account for correlations between the chemically active (valence) and innermore (core) electrons in the framework of the generalized relativistic effective core potential (GRECP) method is suggested. The "correlated" GRECP's (CGRECP's) are generated for the Hg and Pb atoms. Only correlations for the external twelve and four electrons of them, correspondingly, should be treated explicitly in the subsequent calculations with these CGRECP's whereas the innermore electrons are excluded from the calculations. Results of atomic calculations with the correlated and earlier GRECP versions are compared with the corresponding all-electron Dirac-Coulomb values. Calculations with the above GRECP's and CGRECP's are also carried out for the lowest-lying states of the HgH molecule and its cation and for the ground state of the PbO molecule as compared to earlier calculations and experimental data. The accuracy for the vibrational frequencies is increased up to an order of magnitude and the errors for the bond lengths (rotational constants) are decreased in about two times when the correlated GRECP's are applied instead of earlier GRECP versions employing the same innercore-outercore-valence partitioning.

physics.chem-ph↗

arXiv2005

Study of P,T-Parity Violation Effects in Polar Heavy-Atom Molecules

Investigation of P,T-parity nonconservation (PNC) phenomena is of fundamental importance for physics. Experiments to search for PNC effects have been performed on TlF and YbF molecules and are in progress for PbO and PbF molecules. For interpretation of molecular PNC experiments it is necessary to calculate those needed molecular properties which cannot be measured. In particular, electronic densities in heavy-atom cores are required for interpretation of the measured data in terms of the P,T-odd properties of elementary particles or P,T-odd interactions between them. Reliable calculations of the core properties (PNC effect, hyperfine structure etc., which are described by the operators heavily concentrated in atomic cores or on nuclei) usually require accurate accounting for both relativistic and correlation effects in heavy-atom systems. In this paper, some basic aspects of the experimental search for PNC effects in heavy-atom molecules and the computational methods used in their electronic structure calculations are discussed. The latter include the generalized relativistic effective core potential (GRECP) approach and the methods of nonvariational and variational one-center restoration of correct shapes of four-component spinors in atomic cores after a two-component GRECP calculation of a molecule. Their efficiency is illustrated with calculations of parameters of the effective P,T-odd spin-rotational Hamiltonians in the molecules PbF, HgF, YbF, BaF, TlF, and PbO.

physics.atom-ph↗

arXiv2005

Generalized RECPs accounting for Breit effects: uranium, plutonium and superheavy elements 112, 113, 114

The Generalized Relativistic Effective Core Potential (GRECP) method is described which allows one to simulate Breit interaction and finite nuclear models by an economic way and with high accuracy. The corresponding GRECPs for the uranium, plutonium, eka-mercury (E112), eka-thallium (E113) and eka-lead (E114) atoms are generated. The accuracy of these GRECPs and of the RECPs of other groups is estimated in atomic numerical SCF calculations with Coulomb two-electron interactions and point nucleus as compared to the corresponding all-electron Hartree-Fock-Dirac-Breit calculations with the Fermi nuclear charge distribution. Different nuclear models and contributions of the Breit interaction between different shells are studied employing all-electron four-component methods.

physics.chem-ph↗