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M. G. Kozlov

Publications and source records attributed to M. G. Kozlov.

At least 91 records · Page 5Linked to original sources
arXiv2010

Atomic transition frequencies, isotope shifts, and sensitivity to variation of the fine structure constant for studies of quasar absorption spectra

Theories unifying gravity with other interactions suggest spatial and temporal variation of fundamental "constants" in the Universe. A change in the fine structure constant, alpha, could be detected via shifts in the frequencies of atomic transitions in quasar absorption systems. Recent studies using 140 absorption systems from the Keck telescope and 153 from the Very Large Telescope, suggest that alpha varies spatially. That is, in one direction on the sky alpha seems to have been smaller at the time of absorption, while in the opposite direction it seems to have been larger. To continue this study we need accurate laboratory measurements of atomic transition frequencies. The aim of this paper is to provide a compilation of transitions of importance to the search for alpha variation. They are E1 transitions to the ground state in several different atoms and ions, with wavelengths ranging from around 900 - 6000 A, and require an accuracy of better than 10^{-4} A. We discuss isotope shift measurements that are needed in order to resolve systematic effects in the study. The coefficients of sensitivity to alpha-variation (q) are also presented.

astro-ph.CO↗
arXiv2010

Sensitivity of the H3O+ inversion-rotational spectrum to changes in m_e/m_p

Quantum mechanical tunneling inversion transition in ammonia NH3 is actively used as a sensitive tool to study possible variations of the electron-to-proton mass ratio, mu = m_e/m_p. The molecule H3O+ has the inversion barrier significantly lower than that of NH3. Consequently, its tunneling transition occurs in the far-infrared (FIR) region and mixes with rotational transitions. Several such FIR and submillimiter transitions are observed from the interstellar medium in the Milky Way and in nearby galaxies. We show that the rest-frame frequencies of these transitions are very sensitive to the variation of mu, and that their sensitivity coefficients have different signs. Thus, H3O+ can be used as an independent target to test hypothetical changes in mu measured at different ambient conditions of high (terrestrial) and low (interstellar medium) matter densities. The environmental dependence of mu and coupling constants is suggested in a class of chameleon-type scalar field models - candidates to dark energy carrier.

astro-ph.CO↗
arXiv2010

Searching for chameleon-like scalar fields with the ammonia method. II. Mapping of cold molecular cores in NH3 and HC3N lines

(Abridged) In our previous work we found a statistically significant offset Delta V = 27 m/s between the radial velocities of the HC3N(2-1) and NH3(1,1) transitions observed in molecular cores from the Milky Way. This may indicate that the electron-to-proton mass ratio, mu = m_e/m_p, increases by 3x10^{-8} when measured under interstellar conditions with matter densities of more than 10 orders of magnitude lower as compared with laboratory (terrestrial) environments. We now map four molecular cores L1498, L1512, L1517, and L1400K selected from our previous sample in order to estimate systematic effects in Delta V due to possible velocity gradients. We find that in two cores L1498 and L1512 the NH3(1,1) and HC3N(2-1) transitions closely trace the same material and show an offset of Delta V = 26.9 +/- 1.2_stat +/- 3.0_sys m/s throughout the entire clouds. The measured velocity offset, being expressed in terms of Delta mu = (mu_obs - mu_lab)/mu_lab, gives Delta mu = (26 +/- 1_stat +/- 3_sys)x10^{-9}.

astro-ph.CO↗
arXiv2010

Relativistic many-body calculation of low-energy dielectronic resonances in Be-like carbon

We apply relativistic configuration-interaction method coupled with many-body perturbation theory (CI+MBPT) to describe low-energy dielectronic recombination. We combine the CI+MBPT approach with the complex rotation method (CRM) and compute the dielectronic recombination spectrum for Li-like carbon recombining into Be-like carbon. We demonstrate the utility and evaluate the accuracy of this newly-developed CI+MBPT+CRM approach by comparing our results with the results of the previous high-precision study of the CIII system [Mannervik et al., Phys. Rev. Lett. 81, 313 (1998)].

physics.atom-ph↗
arXiv2010

Sensitivity of microwave spectra of deuterated ammonia to variation of electron-to-proton mass ratio

We estimate sensitivity coefficients Q_μto variation of the electron-to-proton mass ratio μfor microwave transitions in partly deuterated ammonia NH2D and ND2H. Because of the mixing between rotational and inversion degrees of freedom the coefficients Q_μstrongly depend on the quantum numbers of the transition. This can be used for astrophysical search for possible variation of the constant μ.

physics.atom-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

Sensitivity of microwave and FIR spectra to variation of fundamental constants

We estimate sensitivity coefficients to variation of the fine-structure constant alpha and electron-to-proton mass ratio mu for microwave Lambda-type transitions in CH molecule and for inversion-rotational transitions in partly deuterated ammonia NH2D. Sensitivity coefficients for these systems are large and strongly depend on the quantum numbers of the transition. This can be used for the search for possible variation of alpha and mu.

astro-ph.CO↗
arXiv2009

Parity nonconservation in electron recombination of multiply charged ions

We discuss a parity nonconserving asymmetry in the cross section of KLL dielectronic recombination of polarized electrons on the hydrogen-like ions with $Z \lesssim 60$. This effect is strongly enhanced because of the near-degeneracy of doubly-excited $2l2l'$ states of opposite parity in He-like ions. For ions with $Z \sim 30$ the asymmetry is of the order of $10^{-9}$. For $Z \approx 48$ a level crossing takes place, leading to the PNC asymmetry of $\pm 5\times 10^{-9}$, which is $10^8$ times greater than the basic strength of the weak interaction in atoms.

physics.atom-ph↗
arXiv2009

Hyperfine-interaction- and magnetic-field-induced Bose-Einstein-statistics suppressed two-photon transitions

Two-photon transitions between atomic states of total electronic angular momentum $J_a=0$ and $J_b=1$ are forbidden when the photons are of the same energy. This selection rule is analogous to the Landau-Yang theorem in particle physics that forbids decays of vector particle into two photons. It arises because it is impossible to construct a total angular momentum $J_{2γ}=1$ quantum-mechanical state of two photons that is permutation symmetric, as required by Bose-Einstein statistics. In atoms with non-zero nuclear spin, the selection rule can be violated due to hyperfine interactions. Two distinct mechanisms responsible for the hyperfine-induced two-photon transitions are identified, and the hyperfine structure of the induced transitions is evaluated. The selection rule is also relaxed, even for zero-nuclear-spin atoms, by application of an external magnetic field. Once again, there are two similar mechanisms at play: Zeeman splitting of the intermediate-state sublevels, and off-diagonal mixing of states with different total electronic angular momentum in the final state. The present theoretical treatment is relevant to the ongoing experimental search for a possible Bose-Einstein-statistics violation using two-photon transitions in barium, where the hyperfine-induced transitions have been recently observed, and the magnetic-field-induced transitions are being considered both as a possible systematic effect, and as a way to calibrate the measurement.

physics.atom-ph↗
arXiv2009

$Λ$-doublet spectra of diatomic radicals and their dependence on fundamental constants

$Λ$-doublet spectra of light diatomic radicals have high sensitivity to the possible variations of the fine structure constant alpha and electron-to-proton mass ratio beta. For molecules OH and CH sensitivity is further enhanced because of the J-dependent decoupling of the electron spin from the molecular axis, where J is total angular momentum of the molecule. When $Λ$-splitting has different signs in two limiting coupling cases a and b, decoupling of the spin leads to the change of sign of the splitting and to the growth of the dimensionless sensitivity coefficients. For example, sensitivity coefficients for the $Λ$-doublet lines J=9/2 of the $Π_{1/2}$ state of OH molecule are on the order of $10^3$.

astro-ph.CO↗
arXiv2009

Development of a configuration-interaction + all-order method for atomic calculations

We develop a theoretical method within the framework of relativistic many-body theory to accurately treat correlation corrections in atoms with few valence electrons. This method combines the all-order approach currently used in precision calculations of properties of monovalent atoms with the configuration-interaction approach that is applicable for many-electron systems. The method is applied to Mg, Ca, Sr, Zn, Cd, Ba, and Hg to evaluate ionization energies and low-lying energy levels.

physics.atom-ph↗
arXiv2009

Ultracold molecules: new probes on the variation of fundamental constants

Ultracold molecules offer brand new opportunities to probe the variation of fundamental constants with unprecedented sensitivity. This paper summarizes theoretical background and current constraints on the variation of fine structure constant and electron-to-proton mass ratio, as well as proposals and experimental efforts to measure the variations based on ultracold molecules. In particular, we describe two novel spectroscopic schemes on ultracold molecules which have greatly enhanced sensitivity to fundamental constants: resonant scattering near Feshbach resonances and spectroscopy on close-lying energy levels of ultracold molecules.

cond-mat.other↗
arXiv2008

Sensitivity coefficients to $α$-variation for fine-structure transitions in Carbon-like ions

We calculate sensitivity coefficients to $α$-variation for the fine-structure transitions (1,0) and (2,1) within $^3P_J[2s^2 2p^2]$ multiplet of the Carbon-like ions C I, N II, O III, Na VI, Mg VII, and Si IX. These transitions lie in the far infrared region and are in principle observable in astrophysics for high redshifts z~10. This makes them very promising candidates for the search for possible $α$-variation on a cosmological timescale. In such studies one of the most dangerous sources of systematic errors is associated with isotope shifts. We calculate isotope shifts with the help of relativistic mass shift operator and show that it may be significant for C I, but rapidly decreases along the isoelectronic sequence and becomes very small for Mg VII and Si IX.

physics.atom-ph↗
arXiv2008

Isotope shift calculations in Ti II

We present an accurate ab initio method of calculating transition energies and isotope shifts in the 3d-transition metals. It extends previous work that combines the configuration-interaction calculation with many-body perturbation theory by including the effective three-body interaction and modification of the energy denominator. We show that these effects are of importance in Ti II. The need to develop methods that can accurately calculate isotope shifts in 3d-transition metals comes from studies of quasar absorption spectra that seek to measure possible variation of the fine-structure constant alpha over the lifetime of the Universe. Isotope shift can also be used to measure isotope abundances in gas clouds in the early Universe, which are needed in order to test models of chemical evolution.

physics.atom-ph↗
arXiv2008

On spatial variations of the electron-to-proton mass ratio in the Milky Way

(Abridged) Radio-astronomical observations of molecular cores in lines of NH3 (J,K)=(1,1), CCS J_N=2_1-1_0, HC3N J=5-4, and N2H+ J=1-0 are used to measure the relative radial velocity offsets, Delta V, between the NH3 (1,1) and other molecular transitions. Robust statistical analysis is applied to the n=207 individual measurements in the Perseus molecular cloud (PC), the Pipe Nebula (PN), and the infrared dark clouds (IRDCs) to deduce the mean value of Delta V and its uncertainty. The measured values of Delta V from the PC, PN, and IRDCs show statistically significant positive velocity shifts between the line centers of NH3 and other molecules. The most accurate estimates are obtained from subsamples of the NH3/CCS pairs observed in the PC (n=21) and the PN (n=8), Delta V = 36+/-7_stat+/-13.5_sys} m/s and 53+/-11_stat+/-13.5_sys m/s, respectively, and from the n=36 NH3/N2H+ and n=27 NH3/HC3N pairs observed in the IRDCs, Delta V = 148+/-32_stat+/-13.6_sys m/s and 115+/-37_stat+/-31_sys m/s, respectively. Being interpreted in terms of the electron-to-proton mass ratio variation, this gives Delta mu/mu = (4-14)10^{-8}, which is an order of magnitude more sensitive than previous astronomical constraints on this quantity.

astro-ph↗
arXiv2008

Mid- and far-infrared fine-structure line sensitivities to hypothetical variability of the fine-structure constant

Sensitivity coefficients to temporal variation of the fine-structure constant alpha for transitions between the fine-structure (FS) sub-levels of the ground states of C I, Si I, S I, Ti I, Fe I, N II, Fe II, O III, S III, Ar III, Fe III, Mg V, Ca V, Na VI, Fe VI, Mg VII, Si VII, Ca VII, Fe VII, and Si IX are calculated. These transitions lie in the mid- and far-infrared regions and can be observed in spectra of high-redshift quasars and infrared bright galaxies with active galactic nuclei. Using FS transitions to study alpha-variation over cosmological timescale allows to improve the limit on $|Δα/α|$ by several times as compared to contemporaneous optical observations ($|Δα/α| < 10^{-5}$), and to suppress considerably systematic errors of the radial velocity measurements caused by the Doppler noise. Moreover, the far infrared lines can be observed at redshifts z > 10, far beyond the range accessible to optical observations (z < 4). We have derived a simple analytical expression which relates the FS intervals and the sensitivity of the FS transitions to the change of alpha.

astro-ph↗
arXiv2008

Studying variation of fundamental constants with molecules

This review article is devoted to application of precision molecular spectroscopy to studies of the possible spatial and temporal variations of the fundamental constants. Both astrophysical observations and laboratory experiments are discussed.

physics.atom-ph↗