arXiv subjects

V. A. Dzuba

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

At least 37 records · Page 2Linked to original sources

arXiv2024

Highly charged ions of heavy actinides as sensitive probes for time variation of the fine structure constant

Highly charged ions of heavy actinides from uranium to einsteinium are studied theoretically to find optical transitions sensitive to the variation of the fine structure constant. A number of promising transitions have been found in ions with ionisation degree $\sim$~10. All these transitions correspond in single-electron approximation to the $6p$ - $5f$ transitions. Many of the transitions are between ground and excited metastable states of the ions which means that they can probably be used as optical clock transitions. Some of the ions have more than one clock transition with different sensitivity to the variation of the fine structure constant $α$. The most promising systems include the Np$^{10+}$, Np$^{9+}$, Pu$^{11+}$, Pu$^{10+}$, Pu$^{9+}$, Pu$^{8+}$, Bk$^{15+}$, Cm$^{12+}$, and Es$^{15+}$ ions.

physics.atom-ph↗

arXiv2023

Cm$^{15+}$ and Bk$^{16+}$ ion clocks with enhanced sensitivity to new physics

We perform calculations of electronic structure of Cm$^{15+}$ and Bk$^{16+}$ ions and demonstrate that they have transitions which combine the features of atomic optical clocks with the enhanced sensitivity to the variations of the fine structure constant $α$. The high sensitivity is due to large nuclear charge $Z$, high ionisation degree $Z_i$ and the effect of {\em level crossing}, which enables optical transitions between states of different configurations. These are the $6p_{1/2}-5f_{5/2} $ and $6p_{1/2}-5f_{7/2} $ transitions in the single valence electron approximation. Variation of $α$ may be due to the interaction with scalar and pseudoscalar (axion) dark matter fields. Therefore, Cm$^{15+}$ and Bk$^{16+}$ clocks are promising candidates to search for these fields.

physics.atom-ph↗

arXiv2023

The Os$^{16+}$ and Ir$^{17+}$ ions as candidates for accurate optical clock sensitive to physics beyond standard model

We perform detailed calculations of the electronic structure of the Os$^{16+}$ ion and demonstrate that it has several metastable states which can be used for very accurate optical clocks. The clocks are highly sensitive to manifestations of the physics beyond standard model, such as time variation of the fine structure constant $α$, interaction with scalar and pseudoscalar (axion) dark matter fields, local Lorentz invariance and local position invariance violations, and interaction of atomic electrons with nucleus mediated by new boson. The latter can be studied by analysing King plot for isotope shifts and its possible non-linearities since Os has 5 stable isotopes with zero nuclear spin. Similar calculations for the Ir$^{17+}$ ion spectra demonstrate very good agreement between theory and experiment. This helps to validate the method of the calculations and demonstrate that both ions are excellent candidates for the search of new physics.

physics.atom-ph↗

arXiv2023

Shift of nuclear clock transition frequency in $^{229}$Th ions due to hyperfine interaction

We calculate hyperfine structure of $^{229}$Th and its ions (Th~IV, Th~III, Th~II, Th~I) to reveal the dependence of the nuclear clock frequency on the hyperfine interaction (hfi). We calculate first and second-order hfi shifts and demonstrate that due to the differences in the hyperfine structure for different ions and for the ground and isomeric nuclear states, the nuclear frequencies in Th~IV, Th~III, Th~II and Th~I are also different. The first-order shift of frequency is large for a particular hyperfine component, but it vanishes after averaging over all hyperfine states. The second-order shift is small but it does not vanish after averaging. It is three to six orders of magnitude smaller than the shift of the nuclear frequencies due to the Coulomb electron-nucleus interaction considered in our previous work (V. A. Dzuba and V. V. Flambaum, arXiv:2309.11176 (2023)). However, it is six to eight orders of magnitude larger than the projected accuracy of the nuclear clock ($10^{-19}$).

physics.atom-ph↗

arXiv2023

Effects of electrons on nuclear clock transition frequency in $^{229}$Th ions

We perform calculations of the energy shift of the nuclear clock transition frequency $^{229}$Th as a function of the number of electrons in Th ion. We demonstrate that the dependence of the nuclear frequency on electron configuration is significant. E.g., removing one electron from the atom leads to relative shift of the nuclear frequency $\sim 10^{-7}$, which is twelve orders of magnitude larger than expected relative uncertainty of the nuclear clock transition frequency ($\sim 10^{-19}$). This leads to difference of the nuclear clock frequencies in Th~IV, Th~III, Th~II and Th~I. The relative change of the nuclear frequency between neutral Th and its bare nucleus is 1\%. We also calculate the field shift constants for isotopic and isomeric shifts of atomic electron transitions in Th ions.

physics.atom-ph↗

arXiv2023

Calculation of hyperfine structure of erbium and fermium

A version of the configuration interaction method, which has been recently developed to deal with large number of valence electrons, has been used to calculate magnetic dipole and electric quadrupole hyperfine structure constants for a number of states of erbium and fermium. Calculations for fermium are done for extracting nuclear moments of Fm isotopes from recent and future measurements. Calculations for erbium, which has electronic structure similar to those of fermium, are done to study the accuracy of the method.

physics.atom-ph↗

arXiv2023

Effect of finite nuclear size on the electric quadrupole hyperfine operator

We present an expression for the operator of the electric quadrupole hyperfine interaction which takes into account finite nuclear size. We compare the results obtained with the use of this operator with those obtained in the standard approach which ignores finite nuclear size. We found that the effect of changing operators on the hyperfine constant $B$ is small in hydrogen-like systems. There is a very significant enhancement of the effect in many-electron atoms caused by the contribution of the large $s_{1/2}-d_{3/2},d_{5/2}$ and $p_{1/2}-p_{3/2}$ off diagonal matrix elements to the core polarisation, correlation and configuration interaction corrections. Similar enhancement takes place for transition amplitudes induced by the electric quadrupole hyperfine interaction.

physics.atom-ph↗

arXiv2023

Prospects for optical clocks combining high sensitivity to new physics with insensitivity to perturbations; the case of Sb$^{+}$, Au$^{+}$, and Hg$^{2+}$

Our study is motivated by the prospect of several metastable states in the Sb$ ^{+} $, Au$ ^{+} $, and Hg$ ^{2+} $ ions being used as possible candidates for optical clocks. We calculate several atomic properties relevant to the development of optical clocks for those clock transitions using two different approaches of relativistic many-body calculations, configuration interaction with single-double coupled-cluster (CI+SD) method, and configuration interaction with perturbation theory (CIPT) method. Our results demonstrate that the relative black body radiation shifts for these transitions are small, $ \sim 10 ^{-16} $. It is also found that there is considerable sensitivity to new physics, as evidenced by a significant enhancement of the effect of the time variation of the fine structure constant $α$ on the frequencies of the clock transitions. The corresponding factor ranges from -5.56 to 2.20. Our results are compared with available previous data.

physics.atom-ph↗

arXiv2023

Calculation of the hyperfine structure of Dy, Ho, Cf, and Es

A recently developed version of the configuration interaction (CI) method for open shells with a large number of valence electrons has been used to study two heavy atoms, californium (Cf, Z= 98) and einsteinium (Es, Z= 99). Motivated by experimental work to measure the hyperfine structure (HFS) for these atoms, we perform the calculations of the magnetic dipole HFS constants $A$ and electric quadrupole HFS constant $B$ for the sake of interpretation of the measurements in terms of nuclear magnetic moment $μ$ and electric quadrupole moment $Q$. For verification of our computations, we have also carried out similar calculations for the lighter homologs dysprosium (Dy, Z= 66) and holmium (Ho, Z= 67), whose electronic structures are similar to Cf and Es, respectively. We have conducted a revision of the nuclear moments of some isotopes of Es leading to an improved value of the magnetic moment of $^{253}$Es [$μ$($^{253}$Es) = 4.20(13)$μ_N$].

physics.atom-ph↗

arXiv2022

Effects of the long-range neutrino-mediated force in atomic phenomena

physics.atom-ph↗

arXiv2022

High-accuracy optical clocks based on group 16-like highly charged ions

We identify laser-accessible transitions in group 16-like highly charged ions as candidates for high-accuracy optical clocks, including S-, Se-, and Te-like systems. For this class of ions, the ground $^{3}P_{J}$ fine structure manifold exhibits irregular (nonmonotonic in $J$) energy ordering for large enough ionization degree. We consider the $|^3P_2\rangle \longleftrightarrow |^3P_0\rangle$ (ground to first-excited state) electric quadrupole transition, performing relativistic many-body calculations of several atomic properties important for optical clock development. All ions discussed are suitable for production in small-scale ion sources and lend themselves to sympathetic cooling and quantum-logic readout with singly charged ions.

physics.atom-ph↗

arXiv2022

Effects of gravity in extra dimensions in atomic phenomena

We use the difference between theory and experiment for energy intervals in simple atomic systems (hydrogen, muonium, positronium and deuteron) to find limits on the size of extra space dimensions in the Arkani-Hamed - Dimopoulos - Dvali model for gravitation potential on short distances. As an additional experimental fact we use absence of the small size gravitational bound states of elementary particles. We demonstrate that the perturbation theory approach does not work and more reliable results are obtained by solving the Dirac equations for an electron in Coulomb and gravitational fields. These results probe smaller distances than distance between nuclei in molecules and the limits are significantly stronger than the limits on the size of extra dimensions obtained using spectra of hydrogen molecules.

physics.atom-ph↗

arXiv2022

Atomic clocks highly sensitive to the variation of the fine structure constant based on Hf II, Hf IV, and W VI ions

We demonstrate that several metastable excited states in Hf$~$II, Hf$~$IV and W$~$VI ions may be good clock states since they are sufficiently long-living and are not sensitive to the perturbations. Cooling E1 transitions are available. Energy levels, Landé $g$-factors, transition amplitudes for electric dipole (E1), electric quadrupole (E2), and magnetic dipole (M1) transitions, lifetimes, and electric quadrupole moments for Hf$~$II, Hf$~$IV, and W$~$VI ions are investigated using a combination of several methods of relativistic many-body calculations including the configuration interaction (CI), linearized coupled-cluster single-doubles (SD) and many-body perturbation theory (CI+SD), and also the configuration interaction with perturbation theory (CIPT). Scalar polarizabilities of the ground states and the clock states have been calculated to determine the black body radiation (BBR) shifts. We have found that the relative BBR shifts for these transitions range between 10$^{-16}$ $-$ 10$^{-18}$. A linear combination of two clock transition frequencies allows one to further suppress BBR. Several $5d$ - $6s$ single-electron clock transitions ensure high sensitivity of the transition frequencies to the variation of the fine structure constant $α$ and may be used to search for dark matter producing this variation of $α$. The enhancement coefficient for $α$ variation reaches $K=8.3$. Six stable isotopes of Hf and 5 stable isotopes in W allow one to make King plots and search for new interactions mediated by scalar particles or other mechanisms.

physics.atom-ph↗

arXiv2022

Long-range parity non-conserving electron-nucleon interaction

As known, electron vacuum polarization by nuclear Coulomb field produces Uehling potential with the range $\hbar/2m_e c$. Similarly, neutrino vacuum polarization by $Z$ boson field produces long range potential $\sim G^2/r^5$ with the large range $\hbar/2m_νc$. Attempts to measure parity-conserving part of this potential produced only limits on this potential which are several orders of magnitude higher than the standard model predictions. We show that parity non-conserving (PNC) part of the neutrino exchange potential $W_L(r)$ gives a significant fraction of the observed PNC effects. Mixed $Z-γ$ electron vacuum polarization produces PNC potential with range $\hbar/2m_e c$, which exceeds the range of the weak interaction by five orders of magnitude. We calculate contribution of the long-range PNC potentials to the nuclear spin independent and nuclear spin dependent PNC effects. The cases of the single-isotope PNC effects and the ratio of PNC effects in different isotopes are considered for Ca, Cs, Ba, Sm, Dy, Yb, Hg, Tl, Pb, Bi, Fr, Ra atoms and ions. Contributions of the long-range PNC potentials ($\sim$1\%) significantly exceed experimental error (0.35\%) for PNC effect in Cs.

hep-ph↗

arXiv2022

Relativistic frequency shifts in Cr, Ti, Fe, Ni, Ca, Na, and V to search for variation in the fine structure constant

Sensitivity of the frequencies of twenty two atomic transitions to the variation of the fine structure constant $α$ is calculated. The findings are to be used in search for possible variation of $α$ across our Galaxy using high quality spectroscopic data for stars similar to our Sun.

physics.atom-ph↗

arXiv2022

Precision determination of isotope shifts in ytterbium and implications for new physics

We report measurements of isotope shifts for the five spinless Yb isotopes on the $6s^2\,^1\textrm{S}_0 \rightarrow 5d6s\,^1\textrm{D}_2$ transition using Doppler-free two-photon spectroscopy. We combine these data with existing measurements on two transitions in Yb$^+$ [Phys. Rev. Lett. 125, 123002 (2020)], where deviation from King-plot linearity showed hints of a new bosonic force carrier at the 3$σ$ level. The combined data strongly reduces the significance of the new-physics signal. We show that the observed nonlinearity in the joint Yb/Yb$^+$ King-plot analysis can be accounted for by the deformation of the Yb nuclei.

physics.atom-ph↗

arXiv2021

Nuclear polarisation and relativistic effects contributions to King plot non-linearity

The effect of nuclear polarisation on the non-linearities of King plot for isotope shift in Ca$^+$, Sr$^+$ and Yb$^+$ ions is studied. These ions are currently used in search for the manifestation of new interaction via non-linearities of King plot. The role of relativistic effects is also studied. The best way to achieve separation of electronic and nuclear variables (which is necessary for the linearity) is to present the field shift as $F"δ\langle r^λ \rangle$, where the value of $λ$ is the result of numerical relativistic calculations ($2γ< λ<2$, $γ= \sqrt{1-(Z/137.036)^2}$). Using this ansatz we demonstrated that the contribution of the relativistic effects to the non-linearity in spherical nuclei is very small.

physics.atom-ph↗

arXiv2021

Theoretical study of electronic structure of hafnium (Hf, Z=72) and rutherfordium (Rf, Z=104) atoms and their ions: Energy levels and hyperfine structure constants

Energy levels, magnetic dipole, and electric quadrupole hyperfine structure of the superheavy element rutherfordium (Rf, $Z$=104) and its first three ions are calculated using a combination of the configuration interaction, coupled-cluster single-doubles, and many-body perturbation theory techniques. The results are to be used in future interpretations of the measurements in terms of nuclear magnetic dipole and electric quadrupole momenta. To have a guide on the accuracy of the study, we perform similar calculations for hafnium (Hf, $Z$=72) and its ions. Hf is a lighter analog of Rf with a similar electronic structure. Good agreement with the experiment for Hf and with available previous calculations of the energy levels of Rf is demonstrated.

physics.atom-ph↗