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result(s) for
"Kozlov, M G"
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A search for varying fundamental constants using hertz-level frequency measurements of cold CH molecules
Many modern theories predict that the fundamental constants depend on time, position or the local density of matter. Here we develop a spectroscopic method for pulsed beams of cold molecules, and use it to measure the frequencies of microwave transitions in CH with accuracy down to 3 Hz. By comparing these frequencies with those measured from sources of CH in the Milky Way, we test the hypothesis that fundamental constants may differ between the high- and low-density environments of the Earth and the interstellar medium. For the fine structure constant we find Δ
α
/
α
=(0.3±1.1) × 10
−7
, the strongest limit to date on such a variation of
α
. For the electron-to-proton mass ratio we find Δ
μ
/
μ
=(−0.7±2.2) × 10
−7
. We suggest how dedicated astrophysical measurements can improve these constraints further and can also constrain temporal variation of the constants.
Some theories predict that fundamental constants may depend on time, position or the local density of matter. Truppe
et al.
compare new precise frequency measurements of microwave transitions in cold CH with Milky Way data, placing a new limit on variation in the fine structure constant.
Journal Article
Exchange-assisted tunneling and enhancement of positron annihilation with inner-shell ellectrons
Synopsis Exchange interaction and correlations radically change behaviour of of a quantum particle in a classically forbidden region. Exchange produces a power-law decay instead of the usual exponential decrease of the wave function. Exchange-assisted tunneling enhances annihilation of positron with inner-shell electrons and produces other observable effects.
Journal Article
Electron recombination with multicharged ions via chaotic many-electron states
Synopsis Electron recombination with multicharged ions that have open f shells (e.g. Au25+ and W20+) is dominated by chaotic many-electron resonances. They cause the fluorescence yield to dominate entirely at low energies leading to an enhancement of the recombination rate up to 1000 times. At higher energies the opening of many autoionization channels leads to a rapid decrease of the fluorescence yield. We apply the statistical theory to express the recombination cross section as a sum over the doorway (dielectronic) resonances.
Journal Article
QED calculations of the E1 transition amplitude in neon-like iron and nickel
We calculated QED corrections to the \\(E1\\) transition amplitudes in Ne-like iron and nickel. For the \\(2p 3d\\) transitions the dominant effect came from the many-electron mixing, or electronic correlations. For the \\(2p 3s\\) transitions the correlation and one-electron effects were comparable and tended to compensate each other. Our ab initio calculations showed that vertex corrections were negligible for both types of transitions. Other QED corrections were accurately reproduced by including effective QEDMOD operator in the many-electron relativistic configuration interaction calculation.
Paper
Methanol isotopologues as a probe for spatial and temporal variations of the electron-to-proton mass ratio
We present results on numerical calculations of the sensitivity coefficients, Qmu, of microwave molecular transitions in (13C)H3OH and CH3(18O)H to the hypothetical variation in the fundamental physical constant mu - the electron-to-proton mass ratio. The invariability of mu in time and space is one of the basic assumptions of the Standard Model of particle physics which can be tested at cosmological scales by means of astronomical observations in the Galaxy and external galaxies. Our calculations show that these two methanol isotopologues can be utilized for such tests since their microwave transitions from the frequency interval 1-100 GHz exhibit a large spread in Qmu values which span a range of -109 < Qmu < 78. We show that the thermal emission lines of (13C)H3OH observed in the star-forming region NGC6334I constrain the variability of mu at a level of 3x10^-8 (1{\\sigma}), which is in line with the most stringent upper limits obtained previously from observations of methanol (CH3OH) and other molecules in the Galaxy.
Paper
Flavor physics of leptons and dipole moments
This chapter of the report of the “Flavor in the era of the LHC” Workshop discusses the theoretical, phenomenological and experimental issues related to flavor phenomena in the charged lepton sector and in flavor conserving CP-violating processes. We review the current experimental limits and the main theoretical models for the flavor structure of fundamental particles. We analyze the phenomenological consequences of the available data, setting constraints on explicit models beyond the standard model, presenting benchmarks for the discovery potential of forthcoming measurements both at the LHC and at low energy, and exploring options for possible future experiments.
Journal Article
Bremsstrahlung on noble gases at low energies
A detailed analysis of the bremsstrahlung spectrum at nonrelativistic electron scattering on argon and xenon is carried out. It is shown that the approximate formulas widely used for the description of bremsstrahlung spectra lead to predictions that significantly differ from the exact results. In the limit when the photon frequency tends to zero, a rigorous proof of the relationship between the spectrum of the bremsstrahlung with a transport cross section of electron scattering on an atom is given. This proof does not require any assumptions about the dependence of the scattering phases on energy. For electron energies lower than the luminescence threshold, it is shown that the predictions for a number of radiated photons obtained by the exact formula are in good agreement with the available experimental data.
Paper
Precision calculation of hyperfine constants for extracting nuclear moments of 229Th
Determination of nuclear moments for many nuclei relies on the computation of hyperfine constants, with theoretical uncertainties directly affecting the resulting uncertainties of the nuclear moments. In this work we improve the precision of such method by including for the first time an iterative solution of equations for the core triple cluster amplitudes into the relativistic coupled-cluster method, with large-scale complete basis sets. We carried out calculations of the energies and magnetic dipole and electric quadrupole hyperfine structure constants for the low-lying states of 229Th^(3+) in the framework of such relativistic coupled-cluster single double triple (CCSDT) method. We present a detailed study of various corrections to all calculated properties. Using the theory results and experimental data we found the nuclear magnetic dipole and electric quadrupole moments to be mu = 0.366(6)*mu_N and Q = 3.11(2) eb, and reducing the uncertainty of the quadrupole moment by a factor of three. The Bohr-Weisskopf effect of the finite nuclear magnetization is investigated, with bounds placed on the deviation of the magnetization distribution from the uniform one.
Paper
The Bohr-Weisskopf effect in the potassium isotopes
The magnetic hyperfine structure constants have been calculated for low-lying levels in neutral potassium atom taking into account the Bohr--Weisskopf (BW) and Breit--Rosenthal (BR) effects. According to our results the \\(4p_{1/2}\\) state of K~I is free from both BR and BW corrections on the level of the current theoretical uncertainties. Using this finding and the measured values of the \\(A(4p_{1/2})\\) constants, we corrected the nuclear magnetic moments for several short-lived potassium isotopes. The BW correction is represented as a product of atomic and nuclear factors. We calculated the atomic factor for the ground state of K I, which allowed us to extract nuclear factors for potassium \\(I^\\pi = 3/2^+\\) isotopes from the experimental data. In this way the application range of the single-particle nuclear model for nuclear-factor calculation in these isotopes has been clarified.
Paper