A. I. Chumakov

PANalytical B.V., Almeloo, Overijssel, Netherlands

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Publications (180)479.48 Total impact

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    ABSTRACT: We measured nuclear forward scattering spectra utilizing the ^{99}Ru transition, 89.571(3) keV, with a notably mixed E2/M1 multipolarity. The extension of the standard evaluation routines to include mixed multipolarity allows us to extract electric and magnetic hyperfine interactions from ^{99}Ru-containing compounds. This paves the way for several other high-energy Mössbauer transitions, E∼90 keV. The high energy of such transitions allows for operando nuclear forward scattering studies in real devices.
    Physical Review Letters 10/2014; 113(14):147601. · 7.73 Impact Factor
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    ABSTRACT: We measured nuclear forward scattering spectra utilizing the Ru-99 transition, 89.571(3) keV, with a notably mixed E2/M1 multipolarity. The extension of the standard evaluation routines to include mixed multipolarity allows us to extract electric and magnetic hyperfine interactions from Ru-99-containing compounds. This paves the way for several other high-energy Mossbauer transitions, E similar to 90 keV. The high energy of such transitions allows for operando nuclear forward scattering studies in real devices.
    Physical Review Letters 10/2014; 113(14):147601. DOI:10.1103/PhysRevLett.113.147601 · 7.73 Impact Factor
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    ABSTRACT: Many Mössbauer spectroscopy (MS) experiments have used a rotating absorber in order to mea-sure the second-order Transverse Doppler (TD) shift, and to test the validity of the Einstein time dilation theory. From these experiments, one may also test the Clock Hypothesis (CH) and the time dilation caused by acceleration. In previous experiments, it was assumed that the rotation of the absorber affects its absorption line by TD shift only. Friedman and Nowik have already predicted that the γ-ray beam finite size dramatically affects the MS absorption line and causes its broad-ening. We provide here explicit formulas to evaluate this broadening. The broadening is linearly proportional to the rotation frequency and to the beam line width at the rotation axis. In addition, we show that the TD shift and the MS line broadening are affected by an additional factor assigned as the alignment shift which is proportional to the frequency of rotation and to the distance between the γ-ray beam center and the rotation axis. This new shift helps to align the disk's axis of rotation to the γ-ray beam's center. To minimize the broadening, one must focus the gamma ray on the axis of the rotating disk and/or to add a slit positioned at the center, to block the rays distant from the rotation axis of the disk. Our experiment, using the 57 F e Synchrotron Mössbauer Source (SMS), currently available at ID18 beam-line of ESRF, with a rotating stainless steel foil, confirmed our predictions. With a slit installed at the rotation axis (reducing the effective beam width from 15.6µm to 5.4µm), one can measure a statistically meaningful absorption spectrum up to 300 Hz, while without a slit, such spectra could be obtainedup to 100Hz only. Thus, both the broadening and the alignment shift are very significant and must be taken into consideration in any rotating absorber experiment. We offer here a method to measure accurately the TD shift and to test the CH.
    Journal of Synchrotron Radiation 09/2014; DOI:10.1107/S1600577515001411 · 3.02 Impact Factor
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    ABSTRACT: Elastic wave velocities of minerals are important for constraining the chemistry, structure and dynamics of the Earth’s mantle based on the comparison between laboratory-based measurements and seismic observations. As the second most abundant phase in the Earth’s lower mantle, (Mg,Fe)O ferropericlase has been the focus of numerous studies measuring the elastic wave velocities using various methods such as Brillouin spectroscopy and ultrasonic measurements. Recently, nuclear inelastic scattering (NIS) has been used to determine elastic wave velocities of iron-bearing phases. However, the elastic wave velocities of ferropericlase obtained using NIS are considerably lower than the velocities obtained by other methods, even at ambient conditions. One possible source of this discrepancy is the local nature of the NIS method. In order to test this hypothesis, we have investigated six ferropericlase samples with various iron contents using NIS. The Debye sound velocities calculated using the conventional method of NIS analysis are consistent with previous results obtained using NIS, yet the values are significantly lower than those obtained using ultrasonics and Brillouin spectroscopy. If the Debye sound velocities are re-calculated based on a mixture of different iron next-neighbour configurations with different compositions, the Debye sound velocities determined by NIS agree well with the results from other methods. Our new model was also successfully applied to high-pressure NIS data taken from the literature. Our results constitute an important step towards a better understanding of how to obtain reliable sound velocities of iron-bearing mantle minerals from NIS measurements.
    Physics of The Earth and Planetary Interiors 04/2014; 229. DOI:10.1016/j.pepi.2013.12.002 · 2.40 Impact Factor
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    ABSTRACT: We have investigated silicate perovskite with composition Mg0.83Fe0.21Al0.06Si0.91O3 relevant for the lower mantle at pressures up to 81 GPa and temperatures up to 2000 K using conventional Mössbauer spectroscopy and synchrotron Nuclear Forward Scattering (NFS) combined with double-sided laser heating in a diamond anvil cell. Room temperature Mössbauer and NFS spectra at low pressure are dominated by high-spin Fe2 +, with minor amounts of Fe3 + and a component assigned to a metastable position of high-spin Fe2 + in the A-site predicted by computational studies. NFS data show a sharp transition (< 20 GPa) from high-spin Fe2 + to a new component with extremely high quadrupole splitting, similar to previous studies. Mössbauer data show the same transition, but over a broader pressure range likely due to the higher pressure gradient. The new Fe2 + component is assigned to intermediate-spin Fe2 +, consistent with previous X-ray emission studies. NFS data at high temperatures and high pressures comparable to those in the lower mantle are consistent with the presence of Fe2 + only in the intermediate-spin state and Fe3 + only in the high-spin state. Our results are therefore consistent with the occurrence of spin crossover only in Fe2 + in Fe-, Al-containing perovskite within the lower mantle.
    Lithos 01/2014; 189. DOI:10.1016/j.lithos.2013.10.022 · 3.65 Impact Factor
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    ABSTRACT: The partial phonon densities of states of iron atoms in the intermetallic compound FeSi have been measured in the temperature range 46-297 K using nuclear resonant inelastic scattering of synchrotron radiation. A significant phonon softening with increasing temperature has been established. The greatest phonon softening for iron atoms is shown to occur in the region of long-wavelength acoustic phonons, for the acoustic branches near the boundary of the Brillouin zone, and for the low-lying weakly dispersive optical branches. The results obtained are analyzed in terms of the views that relate the change in the phonon density of states of iron atoms to the temperature evolution of the electronic density of state for the compound.
    Journal of Experimental and Theoretical Physics 01/2014; 118(2). DOI:10.1134/S1063776114020034 · 0.93 Impact Factor
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    ABSTRACT: We measured the density of vibrational states (DOS) and the specific heat of various glassy and crystalline polymorphs of SiO_{2}. The typical (ambient) glass shows a well-known excess of specific heat relative to the typical crystal (α-quartz). This, however, holds when comparing a lower-density glass to a higher-density crystal. For glassy and crystalline polymorphs with matched densities, the DOS of the glass appears as the smoothed counterpart of the DOS of the corresponding crystal; it reveals the same number of the excess states relative to the Debye model, the same number of all states in the low-energy region, and it provides the same specific heat. This shows that glasses have higher specific heat than crystals not due to disorder, but because the typical glass has lower density than the typical crystal.
    Physical Review Letters 01/2014; 112(2):025502. DOI:10.1103/PhysRevLett.112.025502 · 7.73 Impact Factor
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    ABSTRACT: We report a Mössbauer spectroscopic study of a Fe2+-rich aluminous silicate glass and a Fe3+-rich sodium silicate glass measured in a diamond anvil cell up to 84 GPa. The hyperfine parameters vary smoothly with pressure and are consistent with a gradual increase in coordination number with pressure. Fe2+ and Fe3+ remain in the high-spin state and show no evidence of spin crossover over the measured pressure range. A spin crossover may eventually occur at higher pressures; however the strong thermal broadening of the crossover region due to Boltzmann statistics would prevent any spin crossover from occurring sharply at P,T conditions down to the base of the lower mantle. Our results in combination with recent solid/melt partitioning data in a chondritic system imply that strong preferential partitioning of iron into the melt phase cannot give rise to negatively buoyant melts in the Earthʼs lower mantle.
    Earth and Planetary Science Letters 01/2014; 385:130–136. DOI:10.1016/j.epsl.2013.10.040 · 4.72 Impact Factor
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    ABSTRACT: Magnetic and elastic properties of Ni metal have been studied up to 260 GPa by nuclear forward scattering of synchrotron radiation with the 67.4 keV Mössbauer transition of ^{61}Ni. The observed magnetic hyperfine splitting confirms the ferromagnetic state of Ni up to 260 GPa, the highest pressure where magnetism in any material has been observed so far. Ab initio calculations reveal that the pressure evolution of the hyperfine field, which features a maximum in the range of 100 to 225 GPa, is a relativistic effect. The Debye energy obtained from the Lamb-Mössbauer factor increases from 33 meV at ambient pressure to 60 meV at 100 GPa. The change of this energy over volume compression is well described by a Grüneisen parameter of 2.09.
    Physical Review Letters 10/2013; 111(15):157601. DOI:10.1103/PhysRevLett.111.157601 · 7.73 Impact Factor
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    ABSTRACT: We present a review of our recent work concerning the spin state of Fe2+ and Fe3+ in iron magnesium aluminium silicate perovskite, the most abundant phase in the Earth's interior. Experimental results obtained using Mössbauer spectroscopy (with a radioactive source and a Synchrotron Mössbauer Source) and nuclear forward scattering for a range of different sample compositions in both externally heated and laser-heated diamond anvil cells show clear trends in the variation of hyperfine parameters with pressure and temperature. These trends combined with reported total spin state measurements using X-ray emission spectroscopy on samples of similar composition support the conclusion that Fe2+ undergoes a high-spin to intermediate-spin transition near the top of the lower mantle and an intermediate-spin to low-spin transition near the bottom of the lower mantle. No spin transition is observed to occur in Fe3+ for samples with compositions relevant for the lower mantle.
    High Pressure Research 08/2013; 33(3):663-672. DOI:10.1080/08957959.2013.805217 · 0.93 Impact Factor
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    ABSTRACT: We used nuclear resonant scattering (NRS) of synchrotron radiation to investigate the details of the thickness-induced spin reorientation transition (SRT) in ultrathin epitaxial iron films on W(110), where the thicknesses of the films ranged from 1–5 monolayers. During growth, the magnetization of the Fe film, which was probed by the hyperfine magnetic field, changes from a noncollinear configuration with an out-of-plane magnetic component to the homogeneously magnetized state with the in-plane [1-10] easy direction. The fast acquisition of the experimental NRS spectra combined with the high sensitivity of this technique to the orientation of the hyperfine magnetic fields allowed us to study the magnetic evolution during SRT in detail. Our results reveal the complex character of this transition, which has been intensively studied in the past. The noncollinear magnetic structure appears in the system of the mono-, double-, and trilayer areas that coexist due to deviation from the layer-by-layer growth of iron on W(110). We also report the observation of out-of-plane magnetic anisotropy in the double-layer areas at temperatures as high as 300 K. By comparing the experimental results with density functional theory calculations, we conclude that surface magnetic moments are enhanced by 25%.
    Physical Review B 04/2013; 87:134411. DOI:10.1103/PhysRevB.87.134411 · 3.66 Impact Factor
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    ABSTRACT: Nitrophorins (NPs) occur in the blood-sucking insect Rhodnius prolixus. These proteins use ferric heme to store nitric oxide (NO) in the salivary glands of the insects and transport it to the victim’s tissues, resulting in vasodilation and reduced blood coagulation. In this work we present a nuclear inelastic scattering (NIS) study in order to characterize the iron-NO interaction in the isoform nitrophorin 7 (NP7). The NIS data obtained for NP7 complexed with NO show a strong band at ∼589 cm−1 which is due to modes with significant Fe-NO stretching and bending character. Another conspicuous feature is a significant peak at ∼280 cm−1 in the region where the heme modes occur. Based on a hybrid calculation method, which uses density functional theory and molecular mechanics, the band at ∼280 cm−1 is assigned to heme modes with substantial doming character.
    Hyperfine Interactions 04/2013; 226(1-3):439-443. DOI:10.1007/s10751-013-0982-7 · 0.21 Impact Factor
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    ABSTRACT: The nuclear inelastic scattering signatures of the low spin centres of the methanosulphonate, tosylate and perchlorate salts of the spin crossover polymer ([Fe(II)(4-amino-1,2,4-triazole)3]+2) n have been compared for the pure low-spin phase, for the mixed high-spin and low-spin phases, as well as for Zn(II) diluted samples. Within this series a change in the spectral pattern in the 320–500 cm−1 region is observed involving the decrease of the intensities of a band at ∼320 cm−1 and those over 400 cm−1 as the molar fraction of the low-spin centres decreases. On the basis of the DFT calculations (B3LYP/CEP-31G) this effect is interpreted in terms of vibrational coupling of the iron centres of the same spin.
    Hyperfine Interactions 04/2013; 226(1-3):193-197. DOI:10.1007/s10751-013-0955-x · 0.21 Impact Factor

Publication Stats

2k Citations
479.48 Total Impact Points

Institutions

  • 2014
    • PANalytical B.V.
      Almeloo, Overijssel, Netherlands
  • 1996–2014
    • European Synchrotron Radiation Facility
      • Division of Experiments
      Grenoble, Rhône-Alpes, France
  • 1983–2014
    • Kurchatov Institute
      Moskva, Moscow, Russia
  • 2009
    • Universität Heidelberg
      Heidelburg, Baden-Württemberg, Germany
  • 2005
    • Università degli Studi di Palermo
      Palermo, Sicily, Italy
  • 1995–2000
    • Universität Paderborn
      • Department of Physics
      Paderborn, North Rhine-Westphalia, Germany
  • 1990–1998
    • University of Hamburg
      Hamburg, Hamburg, Germany