arXiv subjects

Mikhail G. Kozlov

Publications and source records attributed to Mikhail G. Kozlov.

At least 19 recordsLinked to original sources

arXiv2026

Testing Exotic Electron-Electron Interactions with the Helium Ionization-Energy Anomaly

Precision atomic spectroscopy provides a sensitive probe of physics beyond the Standard Model. A recently reported $9σ$ theory-experiment discrepancy in the ionization energy of metastable helium has motivated the hypothesis of a new boson mediating exotic electron-electron interactions. Using a model-independent sign-consistency analysis of the induced energy shifts, we show that the sign requirement alone excludes vector-vector and pseudoscalar-pseudoscalar interactions as possible explanations of the anomaly. Incorporating existing constraints together with improved limits obtained here further excludes axial-vector scenarios. Within the single-boson framework considered in this work, only a narrowly constrained scalar-mediated interaction remains viable. The remaining parameter space could be probed, for example, by modest improvements in the determination of the electron gyromagnetic ratio.

physics.atom-ph↗

arXiv2024

Spin-dependent exotic interactions

Novel interactions beyond the four known fundamental forces in nature (electromagnetic, gravitational, strong and weak interactions), may arise due to "new physics" beyond the standard model, manifesting as a "fifth force". This review is focused on spin-dependent fifth forces mediated by exotic bosons such as spin-0 axions and axionlike particles and spin-1 Z' bosons, dark photons, or paraphotons. Many of these exotic bosons are candidates to explain the nature of dark matter and dark energy, and their interactions may violate fundamental symmetries. Spin-dependent interactions between fermions mediated by the exchange of exotic bosons have been investigated in a variety of experiments, particularly at the low-energy frontier. Experimental methods and tools used to search for exotic spin-dependent interactions, such as atomic comagnetometers, torsion balances, nitrogen-vacancy spin sensors, and precision atomic and molecular spectroscopy, are described. A complete set of interaction potentials, derived based on quantum field theory with minimal assumptions and characterized in terms of reduced coupling constants, are presented. A comprehensive summary of existing experimental and observational constraints on exotic spin-dependent interactions is given, illustrating the current research landscape and promising directions of further research.

hep-ph↗

arXiv2024

pCI: a parallel configuration interaction software package for high-precision atomic structure calculations

We introduce the pCI software package for high-precision atomic structure calculations. The standard method of calculation is based on the configuration interaction (CI) method to describe valence correlations, but can be extended to attain better accuracy by including core correlations via many-body perturbation theory (CI+MBPT) or the all-order (CI+all-order) method, as well as QED corrections via QEDMOD. The software package enables calculations of atomic properties, including energy levels, g-factors, hyperfine structure constants, multipole transition matrix elements, polarizabilities, and isotope shifts. It also features modern high-performance computing paradigms, including dynamic memory allocations and large-scale parallelization via the message-passing interface, to optimize and accelerate computations.

physics.atom-ph↗

arXiv2024

Constraints on exotic interactions from scalar spin-spin coupling in tritium deuteride (DT)

A comparison of theoretical and experimental values of the scalar spin-spin interaction ($J$-coupling) in tritium deuteride molecules yield constraints for nucleon-nucleon exotic interactions of the dimensionless coupling strengths $g_Vg_V$, $g_Ag_A$ and $g_pg_p$, corresponding to the exchange of an vector, axial-vector, and pseudoscalar (axionlike) boson. The couplings between proton ($p$) and nucleon ($N$), denoted by $g_V^p g_V^N$, $g_p^p g_p^N$ are constrained to be less than $1.4 \times 10^{-6}$ and $2.7\times 10^{-6}$, respectively, for boson masses around 5 keV. The coupling constant $g_A^p g_A^N$ is constrained to be less than $1.0 \times 10^{-18}$ for boson masses $\leq 100$ eV. It is noteworthy that this study represents the first instance in which constraints on $g_V g_V$ have been established through the analysis of the potential term $V_2 + V_3$ for both tritium deuteride and hydrogen deuteride molecules.

physics.atom-ph↗

arXiv2024

Natural-linewidth measurements of the 3C and 3D soft-x-ray transitions in Ni XIX

We used the monochromatic soft-x-ray beamline P04 at the synchrotron-radiation facility PETRA III to resonantly excite the strongest $2p-3d$ transitions in neon-like Ni XIX ions, $[2p^6]_{J=0} \rightarrow [(2p^5)_{1/2}\,3d_{3/2}]_{J=1}$ and $[2p^6]_{J=0} \rightarrow [(2p^5)_{3/2}\,3d_{5/2}]_{J=1}$, respectively dubbed 3C and 3D, achieving a resolving power of 15\,000 and signal-to-background ratio of 30. We obtain their natural linewidths, with an accuracy of better than 10\%, as well as the oscillator-strength ratio $f(3C)/f(3D)$ = 2.51(11) from analysis of the resonant fluorescence spectra. These results agree with those of previous experiments, earlier predictions, and our own advanced calculations.

physics.atom-ph↗

arXiv2023

Comparison of theory and experiment for radiative characteristics in neutral thulium

Intensities in Tm I emission series originating from a common upper level are measured using a Fourier transform spectrometer. The derived relative transition probabilities within each series are compared to the theoretical predictions obtained from large-scale calculations that combine configuration interaction with many-body perturbation theory. Moreover, the Tm I spectrum recorded in an external magnetic field is analyzed. Our theoretical results well describe the current measurements and show no more than a two-fold difference from previous experimental data on absolute transition probabilities. Additionally, Landé g factors, hyperfine structure constants, and atomic electric quadrupole moments for several levels of interest are computed and compared to experimental observations, where available.

physics.atom-ph↗

arXiv2023

Using parity-nonconserving spin-spin coupling to measure the Tl nuclear anapole moment in a TlF molecular beam

An experiment utilizing a TlF molecular beam is being developed by the CeNTREX collaboration to search for hadronic interactions that violate both time-reversal (T) and parity (P) invariance. Here we propose to use the same beam to look for a T-invariance conserving but P-nonconserving (PNC) effect induced by the anapole moment of the Tl nucleus, via a vector coupling of the two nuclear spins in TlF. To measure the nuclear anapole moment, the dc electric and magnetic fields in CeNTREX are replaced by rf fields resonant with a nuclear spin flip transition. We adapt the relativistic coupled cluster method in a combination with relativistic density functional theory for the calculation of the molecular PNC spin-spin vector coupling constant that links the experimental signal with the anapole moment. The value of the P-conserving spin-spin coupling constant calculated within the same approach is found to be in good agreement with available experimental data.

physics.atom-ph↗

arXiv2022

New Measurement Resolves Key Astrophysical Fe XVII Oscillator Strength Problem

One of the most enduring and intensively studied problems of X-ray astronomy is the disagreement of state-of-the art theory and observations for the intensity ratio of two Fe XVII transitions of crucial value for plasma diagnostics, dubbed 3C and 3D. We unravel this conundrum at the PETRA III synchrotron facility by increasing the resolving power two and a half times and the signal-to-noise ratio thousand-fold compared to our previous work. The Lorentzian wings had hitherto been indistinguishable from the background and were thus not modeled, resulting in a biased line-strength estimation. The present experimental oscillator-strength ratio $R_\mathrm{exp}=f_{\mathrm{3C}}/f_{\mathrm{3D}}=3.51(2)_{\mathrm{stat}}(7)_{\mathrm{sys}}$ agrees with our state-of-the-art calculation of $R_\mathrm{th}=3.55(2)$, as well as with some previous theoretical predictions. To further rule out any uncertainties associated with the measured ratio, we also determined the individual natural linewidths and oscillator strengths of 3C and 3D transitions, which also agree well with the theory. This finally resolves the decades-old mystery of Fe XVII oscillator strengths.

physics.atom-ph↗

arXiv2022

Pseudovector and pseudoscalar spin-dependent interactions in atoms

Hitherto unknown elementary particles can be searched for with atomic spectroscopy. We conduct such a search using a potential that results from the longitudinal polarization of a pseudovector particle. We show that such a potential, inversely proportional to the boson's mass squared, $V \propto 1/M^2$, can stay finite at $M \to 0$ if the theory is renormalizable. We also look for a pseudoscalar boson, which induces a contact spin-dependent potential that does not contribute to new forces searched for in experiments with macroscopic objects, but may be seen in atomic spectroscopy. We extract limits on the interaction constants of these potentials from the experimental spectra of antiprotonic helium, muonium, positronium, helium, and hydrogen.

hep-ph↗

arXiv2021

Probing fast oscillating scalar dark matter with atoms and molecules

Light scalar Dark Matter with scalar couplings to matter is expected within several scenarios to induce variations in the fundamental constants of nature. Such variations can be searched for, among other ways, via atomic spectroscopy. Sensitive atomic observables arise primarily due to possible changes in the fine-structure constant or the electron mass. Most of the searches to date have focused on slow variations of the constants (i.e. modulation frequencies $<$ 1 Hz). In a recent experiment \mbox{[Phys. Rev. Lett. 123, 141102 (2019)]} called WReSL (Weekend Relaxion-Search Laboratory), we reported on a direct search for rapid variations in the radio-frequency band. Such a search is particularly motivated within a class of relaxion Dark Matter models. We discuss the WReSL experiment, report on progress towards improved measurements of rapid fundamental constant variations, and discuss the planned extension of the work to molecules, in which rapid variations of the nuclear mass can be sensitively searched for.

physics.atom-ph↗

arXiv2020

Sensing: Equation One

Spin projection noise sets a limit for the sensitivity of spin-based magnetometers and experiments searching for parity- and time-reversal-invariance-violating dipole moments. The limit is described by a simple equation that appears to have universal applicability.

quant-ph↗

arXiv2020

High Resolution Photoexcitation Measurements Exacerbate the Long-Standing Fe XVII Oscillator Strength Problem

For more than 40 years, most astrophysical observations and laboratory studies of two key soft x-ray diagnostic $2p-3d$ transitions, $3C$ and $3D$, in Fe XVII ions found oscillator strength ratios $f(3C)/f(3D)$ disagreeing with theory, but uncertainties had precluded definitive statements on this much studied conundrum. Here, we resonantly excite these lines using synchrotron radiation at PETRA III, and reach, at a millionfold lower photon intensities, a 10 times higher spectral resolution, and 3 times smaller uncertainty than earlier work. Our final result of $f(3C)/f(3D) = 3.09(8)(6)$ supports many of the earlier clean astrophysical and laboratory observations, while departing by five sigmas from our own newest large-scale ab initio calculations, and excluding all proposed explanations, including those invoking nonlinear effects and population transfers.

physics.atom-ph↗

arXiv2020

Parity nonconserving interactions of electrons in chiral molecules with cosmic fields

Pseudoscalar or pseudovector cosmic fields, that serve as a source of parity ($\mathcal{P}$) violation, are invoked in different models for cold dark matter or in the standard model extension that allows for Lorentz invariance violation. A direct detection of the timelike-component of such fields requires a direct measurement of $\mathcal{P}$-odd potentials or their evolution over time. Herein, advantageous properties of chiral molecules, in which $\mathcal{P}$-odd potentials lead to resonance frequency differences between enantiomers, for direct detection of such $\mathcal{P}$-odd cosmic fields are demonstrated. Scaling behavior of electronic structure enhancements of such interactions with respect to nuclear charge number and the fine-structure constant is derived analytically. This allows a simple estimate of the effect sizes for arbitrary molecules. The analytical derivation is supported by quasi-relativistic numerical calculations in the molecules H$_2$X$_2$ and H$_2$XO with X $=$ O, S, Se, Te, Po. Parity violating effects due to cosmic fields on the C--F stretching mode in CHBrClF are compared to electroweak parity violation and influences of non-separable anharmonic vibrational corrections are discussed. On this basis it was estimated from a twenty year old experiment with CHBrClF that bounds on Lorentz invariance violation as characterized by the parameter $|b^\mathrm{e}_0|$ can be pushed down to the order of $10^{-17}\,\mathrm{GeV}$ in modern experiments with suitably selected molecular system, which will be an improvement of the current best limits by at least two orders of magnitude. This serves to highlight the particular opportunities that precision spectroscopy of chiral molecules provides in the search for new physics beyond the standard model.

physics.chem-ph↗

arXiv2020

Detection of missing low-lying atomic states in actinium

Two lowest-energy odd-parity atomic levels of actinium, 7s^27p 2P^o_1/2, 7s^27p 2P^o_3/2, were observed via two-step resonant laser-ionization spectroscopy and their respective energies were measured to be 7477.36(4) cm^-1 and 12 276.59(2) cm^-1. The lifetimes of these states were determined as 668(11) ns and 255(7) ns, respectively. In addition, these properties were calculated using a hybrid approach that combines configuration interaction and coupled-cluster methods in good agreement. The data are of relevance for understanding the complex atomic spectra of actinides and for developing efficient laser-cooling and ionization schemes for actinium, with possible applications for high-purity medicalisotope production and future fundamental physics experiments with this atom.

physics.atom-ph↗

arXiv2020

Chiral molecules as sensitive probes for direct detection of $\mathcal{P}$-odd cosmic fields

Particular advantages of chiral molecules for direct detection of the time-dependence of pseudoscalar and the timelike-component of pseudovector cosmic fields are highlighted. Such fields are invoked in different models for cold dark matter or in the Lorentz-invariance violating standard model extensions and thus are signatures of physics beyond the standard model. The sensitivity of a twenty year old experiment with the molecule CHBrClF to pseudovector cosmic fields as characterized by the parameter $|b^\mathrm{e}_0|$ is estimated to be $\mathcal{O}(10^{-12}\,\mathrm{GeV})$ and allows to predict the sensitivity of future experiments with favorable choices of chiral molecular probes to be $\mathcal{O}(10^{-17}\,\mathrm{GeV})$, which will be an improvement of the present best limits by at least two orders of magnitude.

hep-ph↗

arXiv2020

Molecular Parity Nonconservation in Nuclear Spin Couplings

The weak interaction does not conserve parity, which is apparent in many nuclear and atomic phenomena. However, thus far, parity nonconservation has not been observed in molecules. Here we consider nuclear-spin-dependent parity nonconserving contributions to the molecular Hamiltonian. These contributions give rise to a parity nonconserving indirect nuclear spin-spin coupling which can be distinguished from parity conserving interactions in molecules of appropriate symmetry, including diatomic molecules. We estimate the magnitude of the coupling, taking into account relativistic corrections. Finally, we propose and simulate an experiment to detect the parity nonconserving coupling using liquid- or gas-state zero-field nuclear magnetic resonance of electrically oriented molecules and show that $^{1}$H$^{19}$F should give signals within the detection limits of current atomic vapor-cell magnetometers.

physics.chem-ph↗

arXiv2020

Fast apparent oscillations of fundamental constants

Precision spectroscopy of atoms and molecules allows one to search for and to put stringent limits on the variation of fundamental constants. These experiments are typically interpreted in terms of variations of the fine structure constant $α$ and the electron to proton mass ratio $μ=m_e/m_p$. Atomic spectroscopy is usually less sensitive to other fundamental constants, unless the hyperfine structure of atomic levels is studied. However, the number of possible dimensionless constants increases when we allow for fast variations of the constants, where "fast" is determined by the time scale of the response of the studied species or experimental apparatus used. In this case, the relevant dimensionless quantity is, for example, the ratio $m_e/\langle m_e \rangle$ and $\langle m_e \rangle$ is the time average. In this sense, one may say that the experimental signal depends on the variation of dimensionful constants ($m_e$ in this example).

physics.atom-ph↗

arXiv2019

Revisiting spin-dependent forces mediated by new bosons: Potentials in the coordinate-space representation for macroscopic- and atomic-scale experiments

The exchange of spin-0 or spin-1 bosons between fermions or spin-polarised macroscopic objects gives rise to various spin-dependent potentials. We derive the coordinate-space non-relativistic potentials induced by the exchange of such bosons, including contact terms that can play an important role in atomic-scale phenomena, and correct for errors and omissions in the literature. We summarise the properties of the potentials and their relevance for various types of experiments. These potentials underpin the interpretation of experiments that search for new bosons, including spectroscopy, torsion-pendulum measurements, magnetometry, parity nonconservation and electric dipole moment experiments.

hep-ph↗