arXiv subjects

N. S. Mosyagin

Publications and source records attributed to N. S. Mosyagin.

At least 19 recordsLinked to original sources

arXiv2025

Laser spectroscopy and CP-violation sensitivity of actinium monofluoride

The apparent invariance of the strong nuclear force under combined charge conjugation and parity (CP) remains an open question in modern physics. Precision experiments with heavy atoms and molecules can provide stringent constraints on CP violation via searches for effects due to permanent electric dipole moments and other CP-odd properties in leptons, hadrons, and nuclei. Radioactive molecules have been proposed as highly sensitive probes for such searches, but experiments with most such molecules have so far been beyond technical reach. Here we report the first production and spectroscopic study of a gas-phase actinium molecule, $^{227}$AcF. We observe the predicted strongest electronic transition from the ground state, which is necessary for efficient readout in searches of symmetry-violating interactions. Furthermore, we perform electronic- and nuclear-structure calculations for $^{227}$AcF to determine its sensitivity to various CP-violating parameters, and find that a realistic, near-term experiment with a precision of 1 mHz would improve current constraints on the CP-violating parameter hyperspace by three orders of magnitude. Our results thus highlight the potential of $^{227}$AcF for exceptionally sensitive searches of CP violation.

physics.atom-ph↗

arXiv2023

The ground-state potential and dipole moment of carbon monoxide: contributions from electronic correlation, relativistic effects, QED, adiabatic, and non-adiabatic corrections

The ground X1Σ+ state potential energy curve (PEC) and dipole moment curve (DMC) of CO molecule have been revisited within the framework of the relativistic coupled-cluster approach, which incorporates non-perturbative single, double, and triple cluster amplitudes (CCSDT) in conjunction with a finite-field methodology. The generalized relativistic pseudo-potential model was used for the effective introducing the relativity in all-electron correlation treatment and accounting the quantum-electrodynamics (QED) corrections within the model-QED-operator approach. The diagonal Born-Oppenheimer correction to PEC has been evaluated using the CCSD approach. The sensitivity of resulting PEC and DMC to variations in basis set parameters and regular intramolecular perturbations were considered as well. The present ab initio results are in a reasonable agreement with their most accurate semi-empirical counterparts.

physics.chem-ph↗

arXiv2023

Electronic structure study of YNbTiO$_6$ vs. CaNb$_2$O$_6$ with U, Pu and minor actinide substitutions using compound-tunable embedding potential method

The compound-tunable embedding potential (CTEP) method is applied to study actinide substitutions in the niobate crystals YNbTiO$_6$ and CaNb$_2$O$_6$. Two one-center clusters centered on Ca and Y are built and 20 substitutions of Ca and Y with U, Np, Pu, Am, and Cm in four different oxidation states were made for each cluster. Geometry relaxation is performed for each resulting structure, and electronic properties are analyzed by evaluating the spin density distribution and X-ray emission spectra chemical shifts. Though the studied embedded clusters with actinides having the same oxidation state are found in general to yield similar local structure distortions, for Am and Cm in high "starting" oxidation states the electron transfer from the environment was found, resulting in decrease of their oxidation states, while for "starting" U$^{\rm III}$ state the electron transfer goes in the opposite direction, resulting in increase of its oxidation state to U$^{\rm IV}$. The U substitutions are additionally studied with the use of multi-center models, which can provide both more structural and electronic relaxation and also include charge-compensating vacancies. For "starting" U$^{\rm VI}$ case, the decrease in oxidation state similar to that of Am$^{\rm VI}$ and Cm$^{\rm VI}$ in one-center clusters is observed in our calculations but in a different way. Since the really synthesized YNbTiO$_6$ structures can not be considered as perfect (periodic) crystals because the Nb and Ti atoms are statistically distributed within them occupying the same Wyckoff positions, different Ti $\leftrightarrow$ Nb substitutions are studied and corresponding structural changes are estimated.

cond-mat.mtrl-sci↗

arXiv2019

Compound-tunable embedding potential method and its application to fersmite crystal

Compound-tunable embedding potential (CTEP) method is proposed. A fragment of some chemical compound, "main cluster" in the present paper, is limited by boundary anions such that the nearest environmental atoms are cations. The CTEP method is based on constructing the embedding potential as linear combination of short-range "electron-free" spherical "tunable" pseudopotentials for cations from nearest environment of the main cluster, whereas the long-range CTEP part consists of Coulomb potentials from optimized fractional point charges centered on both environmental cations and anions. A pilot application of the CTEP method to the fersmite crystal, CaNb$_2$O$_6$, is performed and a remarkable agreement of the electronic density and interatomic distances within the fragment with those of the original periodic crystal calculation is attained. Characteristics of "atoms-in-compounds" which are of great importance for compound of $f$- and $d$-elements (Nb in fersmite) are considered on examples of chemical shifts of $K_{α_{1,2}}\ $ and $K_{β_{1,2}}\ $ lines of X-ray emission spectra in niobium. A very promising potential of this approach in studying variety of properties of point defects containing $f$- and heavy $d$-elements with relativistic effects, extended basis set and broken crystal symmetry considered is discussed.

physics.chem-ph↗

arXiv2019

Compound-tunable embedding potential method and its application to ytterbium fluoride crystals YbF$_2$ and YbF$_3$

Compound-tunable embedding potential (CTEP) method developed in previous works to describe electronic structure of fragments in materials is applied to crystals containing periodically arranged lanthanide atoms, which can have open $4f$ shell. We consider YbF$_2$ and YbF$_3$ as examples such that $4f$ shell is excluded from both the crystal and cluster stages of generating the CTEP. Instead, 10 and 11 valence-electron pseudopotentials for Yb, correspondingly, are applied and the latter treats the $4f$-hole implicitly. At the next stage of the two-component embedded cluster studies of the YbF$_{2,3}$ crystals we apply the 42 valence-electron relativistic pseudopotential for Yb and, thus, $4f$ shell is treated explicitly. A remarkable agreement of the electronic density and interatomic distances within the fragment with those of the original periodic crystal calculation is attained.

physics.chem-ph↗

arXiv2017

Study of the scalar-pseudoscalar interaction in the francium atom

Fr atom can be successively used to search for the atomic permanent electric dipole moment (EDM) [Hyperfine Interactions 236, 53 (2015); Journal of Physics: Conference Series 691, 012017 (2016)]. It can be induced by the permanent electron EDM predicted by modern extensions of the standard model to be nonzero at the level accessible by the new generation of EDM experiments. We consider another mechanism of the atomic EDM generation in Fr. This is caused by the scalar-pseudoscalar nucleus-electron neutral current interaction with the dimensionless strength constant, $k_{T,P}$. Similar to the electron EDM this interaction violates both spatial parity and time-reversal symmetries and can also induce permanent atomic EDM. It was shown in [Phys. Rev. D 89, 056006 (2014)] that the scalar-pseudoscalar contribution to the atomic EDM can dominate over the direct contribution from the electron EDM within the standard model. We report high-accuracy combined all-electron and two-step relativistic coupled cluster treatment of the effect from the scalar-pseudoscalar interaction in the Fr atom. Up to the quadruple cluster amplitudes within the CCSDT(Q) method were included in correlation treatment. This calculation is required for the interpretation of the experimental data in terms of $k_{T,P}$. The resulted EDM of the Fr atom expressed in terms of $k_{T,P}$ is $d_{\rm Fr}= k_{T,P} \cdot 4.50\cdot10^{-18} e\cdot {\rm cm}$, where $e$ is the charge of the electron. The value of the ionization potential of the $^2S_{1/2}$ ground state of Fr calculated within the same methods is in a very good agreement with the experiment.

physics.atom-ph↗

arXiv2015

TaN molecule as a candidate to search for New physics

It is demonstrated that the TaN molecule is the best candidate to search for T,P-violating nuclear magnetic quadrupole moment (MQM), it also looks promising to search for other T,P-odd effects. We report results of coupled-cluster calculations of T,P-odd effects in TaN produced by the Ta nucleus MQM, electron electric dipole moment (EDM), scalar$-$pseudoscalar nucleus$-$electron interactions, also of the molecule-axis hyperfine structure constant and dipole moment. Nuclear calculations of $^{181}$Ta MQM are performed to express the T,P-odd effect in terms of the strength constants of T,P-odd nuclear forces, proton and neutron EDM, QCD parameter $θ$ and quark chromo-EDM.

physics.atom-ph↗

arXiv2014

Calculation of the parity and time reversal violating interaction in ^{225}RaO

The 10-electron generalized relativistic effective core potential and the corresponding correlation spin-orbital basis sets are generated for the Ra atom and the relativistic coupled cluster calculations for the RaO molecule are performed. The main goal of the study is to evaluate the P,T-odd parameter X characterized by the molecular electronic structure and corresponding to a "volume effect" in the interaction of the ^{225}Ra nucleus Schiff moment with electronic shells of RaO. Our final result for X(^{225}RaO) is -7532 which is surprisingly close to that in ^{205}TlF but has different sign. The obtained results are discussed and the quality of the calculations is analyzed. The value is of interest for a proposed experiment on RaO [PRA 77, 024501 (2008)] due to a very large expected Schiff moment of the ^{225}Ra nucleus.

physics.atom-ph↗

arXiv2014

Ab initio study of radium monofluoride, RaF, as a candidate to search for P- and T,P- violation effects

Relativistic ab initio calculations have been performed to assess the suitability of RaF for experimental search of P- and T,P-violating interactions. The parameters of P- and T,P-odd terms of the spin-rotational Hamiltonian have been calculated for the ${^2}Σ$ electronic ground state of RaF molecule. They include the parameter $W_a$, which is critical in experimental search for nuclear anapole moment and the parameters $W_d$ and $W_{\rm SP}$ required to obtain restrictions on the electric dipole moment of the electron and T,P-odd scalar-pseudoscalar interactions, respectively. The parameter $X$ corresponding to the "volume effect" in the T,P$-$odd interaction of the $^{223}$Ra nuclear Schiff moment with electronic shells of RaF has also been computed. Spectroscopic and hyperfine structure constants for $^{223}$RaF and $^{223}$Ra$^+$ have been computed as well, demonstrating the accuracy of the methods employed.

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↗

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↗