K. M. Salikhov

Kazan (Volga Region) Federal University, Kasan, Tatarstan, Russia

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Publications (127)164.59 Total impact

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    ABSTRACT: The energy transfer mechanism, which provides the feeding of the excited 5D4 level of Tb(III), has been studied by photoluminescence spectroscopy in the Tb(III) complex with p-sulfonato-thiacalix[4]arene doped into the silica nanoparticles. The quantitative evaluation of the rate constants of each energy transfer step highlights two channels of the energy transfer from the singlet ligand-centered level to the 5D4 level. The channel one occurs via the triplet ligand level S1→T1→5D4, the second channel comes about via the higher levels of Tb(III) S1→5D3→5D4. The latter channel determines the rate of the luminescence decay of the 5D4 level. The high luminescence efficiency and enhanced thermo- and photo-stabilities make the Tb(III) complexes doped into the silica nanoparticles a promising nanomaterial for medical and bioanalytical applications.
    Journal of Luminescence 01/2015; 157:158–162. DOI:10.1016/j.jlumin.2014.08.050 · 2.37 Impact Factor
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    ABSTRACT: Kinetic equations for the spin density matrix which take into account binary collisions and a method of calculating the spin exchange effective radius have been generalized to the case of dilute solutions of charged paramagnetic particles. The effective radius of the spin exchange and rate constant of the bimolecular spin exchange between charged paramagnetic particles in solutions have been calculated numerically. Calculations have been performed under the assumption that the exchange interaction is isotropic and decays exponentially with the increase in the distance between radicals, and the solution has a given dielectric permittivity and Debye screening radius. De-pendences of the spin exchange rate constant on the mutual diffusion coeffi-cient, exchange and electrostatic interactions parameters have been found numerically. The theory has been applied to experimental results taken from the literature. The rate constant of the spin exchange between radicals of like charge found from the experiment and calculated within the developed theory are in good qualitative agreement.
    Applied Magnetic Resonance 10/2014; 45(7):911. DOI:10.1007/s00723-014-0571-1 · 1.15 Impact Factor
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    ABSTRACT: The study of the terbium(III) and gadolinium(III) βdiketonate complexes by photoluminescence spectroscopy reveals considerable changes of the photophysical properties of the complexes under UV laser irradiation. The measurements show the enhancement of the luminescence intensities in the vitrified transparent film of the terbium(III) complex as well as the gadolinium(III) complex under the 337 nm laser irradiation at room temperature. The irradiated film of the terbium(III) complex restores the initial photophysical properties after heating close to the melting temperature (~353 K) and cooling. We did not observe any change of the luminescent properties of the irradiated film for months. These features can be used for the design of new lanthanide-based photostable systems with laser control of the luminescence intensity.
    Optical Materials 09/2014; DOI:10.1016/j.optmat.2014.07.027 · 2.08 Impact Factor
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    ABSTRACT: The current theory of three-pulse electron double resonance (PELDOR) has been generalized to the case, when paramagnetic particles (spin labels) in pairs or groups have the electron paramagnetic resonance (EPR) spectra, which overlap essentially or coincide. The PELDOR signal modulation induced by the dipole–dipole interaction between paramagnetic spin ½ particles in pairs embedded in disordered systems has been analyzed comprehensively. It has been shown that the PELDOR signal contains additional terms in contrast to the situation considered in the current theory, when the EPR spectra of the spin labels in the pairs do not overlap. In disordered systems, the pairs of spin labels have the characteristic dipolar interaction frequency. According to the current theory for pairs of spin labels, the PELDOR signal reveals the modulation with this characteristic frequency. The additional terms, which are obtained in this work, do not change the modulation frequency of the PELDOR signal for pairs of spin labels. However, these additional terms should be taken into account when analyzing the amplitude of the PELDOR signal and the amplitude of the modulation of the PELDOR signal. The consistent approach to treating the PELDOR data for the groups containing three or more spin labels has been outlined on the basis of the results for pairs of spin labels. It has been also analyzed how the spin flips and molecular motion or molecular isomerization can affect the manifestation of the interaction between the spin labels in PELDOR experiments. PELDOR experiments for the stable biradicals (biradicals I containing 1-oxyl-2,2,5,5-tetramethylpyrroline-3-yl spin labels and biradicals II containing 3-imidazoline spin labels) have been performed. The results have been interpreted within the theory developed in this work.
    Applied Magnetic Resonance 06/2014; 45(6):573-619. DOI:10.1007/s00723-014-0541-7 · 1.15 Impact Factor
  • K. M. Salikhov
    Applied Magnetic Resonance 04/2014; 45(4). DOI:10.1007/s00723-014-0532-8 · 1.15 Impact Factor
  • K. M. Salikhov, I. T. Khairuzhdinov
    Applied Magnetic Resonance 01/2014; 46(1):67-83. DOI:10.1007/s00723-014-0609-4 · 1.15 Impact Factor
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    ABSTRACT: We investigate a possibility to enhance the coherence time of electron spins in magnetic molecular complexes by application of the Carr-Purcell-Meiboom-Gill (CPMG) multiple microwave pulse sequence. Our theoretical analysis shows that the CPMG sequence can efficiently suppress the spin decoherence channel arising due to spectral diffusion induced by a random modulation of the hyperfine interaction which is an important source of the spin dephasing in molecular magnets. We confirm this by employing the CPMG protocol in pulse electron spin resonance experiments on model binuclear 1,2-diphosphacyclopentadienyl manganese complexes.We show that, compared to the standardly used two-pulse primary spin-echo technique, the CPMG experiment can boost the phase memory time up to one order of magnitude, bringing it to above 10 μs at low temperatures. This finding may be important for the implementation of quantum computation protocols on molecular magnets.We discuss a possible interesting analogy with the Zeno’s paradox in quantum theory (the Zeno quantum effect), which could be implicit in the CPMG experiment.
    Physical Review B 09/2013; 88:094418. DOI:10.1103/PhysRevB.88.094418 · 3.66 Impact Factor
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    Kev M. Salikhov
    Applied Magnetic Resonance 08/2013; 44(8). DOI:10.1007/s00723-013-0480-8 · 1.15 Impact Factor
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    ABSTRACT: Electron Paramagnetic Resonance (EPR) spectra of the nitroxide spin probe 3β-doxyl-5α-cholestane (CSL) are studied as functions of the molar concentration, c, and the temperature, T, in a series of n-alkanes. The results are compared with a similar study of a much smaller spin probe, perdeuterated 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (pDT). The Heisenburg spin exchange (HSE) rate constants, K(ex) , of CSL are similar in hexane, octane and decane, and are about one-half of those for pDT in the same solvents. They are also about one-half of the Stokes-Einstein-Perrin (SEP) prediction. This reduction in HSE efficiency is attributed to an effective steric factor, f(eff) , which was evaluated by comparing the results with the Stokes-Einstein-Perrin prediction or with pDT is f(eff) = 0.49 ± 0.03, independent of temperature. The unpaired spin density in CSL is localized near one end of the long molecule, so the exchange integral, J , leading to HSE, is expected to be large in some collisions and small in others; thus, J is modeled by an ideal distribution of values of J =J(0) with probability f and J = zero with probability (1-f). Due to rotational and translation diffusion during contact and between re-encounters of the probe, the effective steric factor is predicted to be f(eff) = f(1/2) . Estimating the fraction of the surface of CSL with rich spin density, yields a theoretical estimate of f(eff) = 0.59 ± 0.08, in satisfactory agreement with experiment. HSE is well described by simple hydrodynamic theory, with only a small dependence on solvent-probe relative sizes at the same value of T/η, where η is the viscosity of the solvent. This result is probably due to a fortuitous interplay between long- and short-range effects that describe diffusion processes over relatively large distances. In contrast, dipole-dipole interactions (DD) as measured by the line broadening, B(dip) , and the mean time between re-encounters within the cage, τ(RE), vary significantly with the solvent-probe size ratio at the same value of T/η. For these phenomena, dominated by short-range diffusion, the reciprocal fractional free volume ,V(0)/V(f) provides a better description of the diffusion. Thus B(dip) and τ(RE) form common curves when plotted vs. V(0)/V(f). As a result, the fractional broadening by DD occurs at an order of magnitude higher values of T/η for CSL compared with pDT.
    The Journal of Physical Chemistry A 11/2012; 116(51). DOI:10.1021/jp310297d · 2.78 Impact Factor
  • M. Yu. Volkov, K. M. Salikhov
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    ABSTRACT: A method of elaborating pulse sequences performing unitary transformations on the basis of their transformation matrices has been developed. For the first time the pulse protocols performing two-qubit quantum logical operations in electron spin systems have been obtained.
    Applied Magnetic Resonance 12/2011; 41(2-4). DOI:10.1007/s00723-011-0297-2 · 1.15 Impact Factor
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    ABSTRACT: We report a pulse electron spin resonance study of binuclear Mn molecular complexes whose magnetic properties are controlled by the ligand substitution. An electron spin echo in these complexes in the solid phase and also diluted in a frozen solution matrix was detected, and the spin decoherence time T2 of Mn spins at different temperatures was determined. We observe a simple exponential T2 relaxation in the latter samples and a nonexponential relaxation process in the former ones. The data analysis establishes the hyperfine coupling to the protons as an important source of the electron spin decoherence. Furthermore, the data clearly suggest an important role of the intermolecular spin-spin coupling for the T2 relaxation. The influence of both mechanisms should be considered as limiting factors for coherent spin manipulation in molecular magnets with regard to their possible application for quantum computing.
    Physical review. B, Condensed matter 09/2011; 84(9). DOI:10.1103/PhysRevB.84.092402 · 3.66 Impact Factor
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    ABSTRACT: The phase behavior of a self-organizing system based on the nonionic surfactant of decaethylene glycol monodecyl ether-lanthanum nitrate hexahydrate-water and decanol is presented. A system phase diagram was constructed. The concentration, temperature ranges of existence and types of liquid crystal phases were established. Analysis of structural changes during the phase transitions hexagonal phase-lamellar phase-isotropic liquid was made on the basis of data obtained by viscosimetry and self-diffusion NMR.
    Russian Journal of Physical Chemistry 05/2010; 84(5):802-807. DOI:10.1134/S003602441005016X · 0.49 Impact Factor
  • K. M. Salikhov
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    ABSTRACT: This report presents a comprehensive analysis of the contributions of the Heisenberg exchange and dipole–dipole interactions in diluted solutions of nitroxide radicals to the shape of their electron paramagnetic resonance (EPR) spectra taking into account all coherence transfer processes. It is shown that these contributions interfere. The approaches to obtain the molecular-kinetic and exchange integral parameters by analyzing the EPR spectrum dependence on the radical concentration and the solvent viscosity are discussed.
    Applied Magnetic Resonance 05/2010; 38(2):237-256. DOI:10.1007/s00723-010-0128-x · 1.15 Impact Factor
  • Yuri E. Kandrashkin, Kev M. Salikhov
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    ABSTRACT: Quantum teleportation of electron spins in the modified photosynthetic reaction centers is investigated numerically. The output of the teleported state is analyzed as a signal of the primary spin echo. The simulations of the model systems clarifying the role of different contributions to the signal are described. Requirements for the successful teleportation, including the recombination rates, Zeeman and spin–spin interactions are found. The variation of the teleportation scheme is discussed.
    Applied Magnetic Resonance 01/2010; 37(1):549-566. DOI:10.1007/s00723-009-0081-8 · 1.15 Impact Factor
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    Klaus Möbius, Kev M. Salikhov
    Applied Magnetic Resonance 01/2010; 37(1):1-4. DOI:10.1007/s00723-009-0040-4 · 1.15 Impact Factor
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    ABSTRACT: The results of the femtosecond four-wave mixingmeasurements performed on the CdS crystal at room temperature are reported. The dephasing time Td = 180 fs was obtained. The anti-Stokes shift of the primary photon echo spectrum with respect to the excitation spectrum was observed. The some peculiarities of the coherent responses decay curves indicate that this optical dephasing is due to the exciton-exciton interaction. The stimulated photon echo decay curves appear to have a fast decay component (the time constant of approximately 4.5 ps) in case the energy of exciting pulses exceeds the threshold value of 0.4 μ J. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA)
    Laser Physics Letters 09/2009; 6(9):644 - 646. DOI:10.1002/lapl.200910054 · 2.96 Impact Factor
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    R. B. Zaripov, R. M. Aminova, K. M. Salikhov
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    ABSTRACT: Manifestations of the hyperfine interaction of paramagnetic particles in their electron spin echo signal decay were comprehensively discussed. Mechanochemically activated calcium gluconate was studied using electron spin echo modulation phenomenon and electron-nuclear double resonance techniques and quantum-chemical calculations. Three possible structures are obtained for free radicals in calcium gluconate. To specify the structure of radicals, further investigations are needed.
    Applied Magnetic Resonance 02/2009; 35(2):337-358. DOI:10.1007/s00723-008-0165-x · 1.15 Impact Factor
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    ABSTRACT: Electron paramagnetic resonance (EPR) spectra of the spin-correlated charge-separated states in photosynthetic reaction centers were numerically simulated with the unresolved hyperfine structure of the EPR lines treated, for the first time exactly, by the Monte Carlo method. The parallel computers with distributed-memory-oriented program tools were elaborated to implement these calculations. The results obtained were compared with those for the unresolved hyperfine structure of the EPR lines taken into account in the framework of a conventional approximate description (the convolution method). It is shown that both approaches lead to practically the same transient EPR spectral shapes in W- and Q-bands, while in the X-band they lead to a noticeably different spectrum shape. Our results show that the shape of the EPR spectra detected at the magnetic fields around 300 mT (X-band EPR) can be simulated well only by the Monte Carlo method, while at higher magnetic fields (Q- and W-bands) the experimental EPR spectra can be simulated reasonably well by the convolution approximation.
    Applied Magnetic Resonance 11/2008; 35(1):113-125. DOI:10.1007/s00723-008-0138-0 · 1.15 Impact Factor
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    ABSTRACT: Some results of femtosecond echo experiments on polyvinylbutyral polymer films doped with phtalocyanine molecules at high (up to room) temperatures are reported. Special attention is paid to the stimulated femtosecond photon echo (SFPE), which was observed in a solid-state medium at room temperature for the first time. A decay curve of the SFPE signal has been obtained and theoretically analyzed. The results of the analysis indicate that the random interaction between impurity molecules and quasi-localized low-frequency vibration modes in an amorphous matrix plays the dominant role in the character of optical dephasing at high temperatures.
    Bulletin of the Russian Academy of Sciences Physics 07/2008; 72(7):1019-1021. DOI:10.3103/S1062873808070381

Publication Stats

656 Citations
164.59 Total Impact Points

Institutions

  • 2014
    • Kazan (Volga Region) Federal University
      Kasan, Tatarstan, Russia
  • 1971–2014
    • Russian Academy of Sciences
      • • Institute of Chemical Kinetics and Combustion
      • • A.E. Arbuzov Institute of Organic and Physical Chemistry Kazan
      • • Zavoisky Physical-Technical Institute, Kazan Branch
      Moskva, Moscow, Russia
  • 1998
    • Freie Universität Berlin
      • Institute of Experimental Physics
      Berlin, Land Berlin, Germany
  • 1983–1989
    • Novosibirsk State University
      Novo-Nikolaevsk, Novosibirsk, Russia
  • 1988
    • University of Leipzig
      Leipzig, Saxony, Germany
  • 1982
    • Altai Mir University
      Altayskiy, Altayskiy, Russia