G. V. Smirnov
Kurchatov Institute
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Hyperfine Interactions | 1996
G. V. Smirnov
The principal ideas of the theory and the main results of the experimental studies of the coherent resonant scattering ofγ-radiation by nuclear ensembles in matter are briefly over-viewed. An analysis of transmission of the Mössbauerγ-radiation and of synchrotron radiation through a nuclear resonant medium is suggested using an approach based on the optical theory. The feasibilities of the nuclear resonant scattering of synchrotron radiation as a new technique for studying the hyperfine interactions and some other phenomena of the physics of condensed matter are considered.
Journal of Synchrotron Radiation | 2012
Vasily Potapkin; Aleksandr I. Chumakov; G. V. Smirnov; Jean‐Philippe Celse; R. Rüffer; Catherine McCammon; Leonid Dubrovinsky
The design of a (57)Fe Synchrotron Mössbauer Source (SMS) for energy-domain Mössbauer spectroscopy using synchrotron radiation at the Nuclear Resonance beamline (ID18) at the European Synchrotron Radiation Facility is described. The SMS is based on a nuclear resonant monochromator employing pure nuclear reflections of an iron borate ((57)FeBO(3)) crystal. The source provides (57)Fe resonant radiation at 14.4 keV within a bandwidth of 15 neV which is tunable in energy over a range of about ±0.6 µeV. In contrast to radioactive sources, the beam of γ-radiation emitted by the SMS is almost fully resonant and fully polarized, has high brilliance and can be focused to a 10 µm × 5 µm spot size. Applications include, among others, the study of very small samples under extreme conditions, for example at ultrahigh pressure or combined high pressure and high temperature, and thin films under ultrahigh vacuum. The small cross section of the beam and its high intensity allow for rapid collection of Mössbauer data. For example, the measuring time of a spectrum for a sample in a diamond anvil cell at ∼100 GPa is around 10 min, whereas such an experiment with a radioactive point source would take more than one week and the data quality would be considerably less. The SMS is optimized for highest intensity and best energy resolution, which is achieved by collimation of the incident synchrotron radiation beam and thus illumination of the high-quality iron borate crystal within a narrow angular range around an optimal position of the rocking curve. The SMS is permanently located in an optics hutch and is operational immediately after moving it into the incident beam. The SMS is an in-line monochromator, i.e. the beam emitted by the SMS is directed almost exactly along the incident synchrotron radiation beam. Thus, the SMS can be easily utilized with all existing sample environments in the experimental hutches of the beamline. Owing to a very strong suppression of electronic scattering for pure nuclear reflections (∼10(-9)), SMS operation does not required any gating of the prompt electronic scattering. Thus, the SMS can be utilized in any mode of storage ring operation.
Hyperfine Interactions | 1999
G. V. Smirnov
The process of nuclear resonant scattering resonant scattering is considered on the basis of an optical model. The coherent properties coherent properties of the radiation and scattering mechanism are described. The complementary pictures of γ-ray resonant scattering in energy and time domains are presented. Special attention is paid to scattering of a γ quantum by an ensemble of nuclei. The central concept of the theory of nuclear resonant scattering, the nuclear exciton, nuclear exciton as a delocalized nuclear excitation, is described in detail. It is shown that both temporal and spatial aspects of coherence play a crucial role in the evolution of the nuclear exciton. A large place is given to the analysis of resonant scattering of synchrotron radiation by nuclear ensembles.
Hyperfine Interactions | 1992
J. M. Knudsen; M. B. Madsen; Morten Tange Olsen; L. Vistisen; Chr. Bender Koch; Steen Mørup; E. Kankeleit; G. Klingelhöfer; E. N. Evlanov; V. N. Khromov; L. M. Mukhin; O. F. Prilutski; B. Zubkov; G. V. Smirnov; J. Juchniewicz
A Mössbauer spectrometer is included in the preliminary payload of a rover to be placed on the surface of Mars in the Soviet mission to the planct in 1996/1,2/. In counection with the American planctary program it has also been suggested to construct a Mössbauer spectrometer to be landed on Mars /3, 4/. The objective is to study the iron compounds of the Martian soil and rocks by backscattering Mössbauer spectroscopy. The paper describes the significance of the element iron in the study of the evolution of the planetary system and what we might expect to learn from Mössbauer spectroscopy of the surface materials of Mars. The study of Mars is expected to expand substantially in the coming decades, probably culminating with a manned flight to the planet. The international Mössbauer community may contribute significantly to the preparation of these events.
Hyperfine Interactions | 1986
G. V. Smirnov
ConclusionAl though the experimental studies of coherent phenomena were started even in early years after the discovery of the Mößbauer effect, this direction has been progressively developed, perhaps, in the last decade only. Looking back, we see the experimental development up to now divided into three main stages. The years 1960–1968 comprise the first manifestations of the coherent nuclear resonant scattering; 1969–1975 — the observations of pure nuclear diffraction and the suppression effect in the non-elastic channel, the estimation of scales of coherency conservation in space and in time and, finally, 1975–1985 years — the epoch of perfect crystals; the proof of enhancement of the role of radiative processes in coherent interaction of γ-rays with nuclei in large volumes, the comprehensive study of properties of a collective coherent nuclear γ-resonance, the intersting first applications of the methods of nuclear diffraction of Mößbauer rays.The recent success in filtering Mößbauer quanta out of the synchrotron radiation marks the beginning of a new stage. Now the field of nuclear resonance diffraction might cease to be the oxotic domain of a few physicists and might be activated by the contributions of many people — and then we shall hopefully witness a new collective phenomenon.
Journal of Physics C: Solid State Physics | 1980
U van Burck; R L Mossbauer; G. V. Smirnov; H J Maurus
The angular and energy dependence of the dynamical diffraction of gamma rays was studied experimentally in the symmetric Bragg case. Mossbauer diffraction spectra were measured with high angular resolution in pure nuclear Bragg reflection of a nearly perfect 57FeBO3 single crystal. In the spectrum taken at the exact Bragg position, very broad hyperfine resonance peaks were observed. In the spectra just above and below the Bragg angle the reflection peaks were much smaller and were shifted to energy positions above and below resonance respectively. The results were interpreted by means of the dynamical theory and compared with computer calculations. The measurements represent the first direct observation of the enhancement of nuclear resonance scattering in the case of a thick crystal reflection. Furthermore the angular dependence of the resonance scattering by a perfect single crystal has been measured for the first time.
Journal of Physics: Condensed Matter | 1992
Yu. V. Shvyd'ko; G. V. Smirnov
Nuclear resonant scattering of gamma -radiation in the forward direction was studied in a vibrated target. Special attention was given to revealing the enhanced yield into the radiative channel of the nuclear reaction due to coherent scattering. The radiative channel in the resonance scattering of 14.4 keV gamma -quanta by 57Fe nuclei normally amounts to only 10.9%. The remaining part of the scattering goes into the conversion channel. The nuclear target used in the experiment (stainless steel enriched in 57Fe nuclei) was completely opaque to the incident resonant gamma -radiation with frequency omega s. When the target started to vibrate with frequency Omega /2 pi =23.79 MHz, it remained opaque to the primary radiation, whereas intense secondary radiation at new frequencies emerged from the target in the forward direction. The omega s+ Omega and omega s- Omega spectral components dominated in the emission spectrum and their total relative intensity reached 29.0+or-1.5% of the incident gamma -radiation intensity. It was shown theoretically that such an essential enlargement of the yield into the radiative channel of the nuclear reaction was possible owing to conditions of coherent enhancement of the radiative channel and anomalously weak resonance absorption, which were provided by vibrating the target. The effect can be observed if the nuclei move in unison in the coherence volume. All experimental data were well fitted in the frame of the chosen theoretical model.
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms | 1999
J. Jäschke; H. D. Rüter; E. Gerdau; G. V. Smirnov; Wolfgang Sturhahn; J. Pollmann
Abstract A single line linear polarized source of 14.4 keV is realized in a conventional Mossbauer setup. In combination with the dichroism of a magnetized 57FeBO3 or α-57Fe absorber a single line unpolarized 57Co Cr - or 57Co Pt -source delivers ⩾90% linear polarized radiation and about 25% of its primary intensity. The optimal value of the internal magnetic field of each absorber is selected by temperature adjustment. Calculations and measurements are in good agreement.
Journal of Non-crystalline Solids | 2001
Quentin A. Pankhurst; Neil S. Cohen; Luis Fernández Barquín; M.R.J. Gibbs; G. V. Smirnov
Abstract Moment canting, a phenomenon where the atomic moments in a soft magnet do not completely align with an applied field of substantial magnitude, has been measured in field annealed (FA) and stress relieved (SR) ribbons of the amorphous alloy Fe78Si9B13. Measurements were made using a synchrotron Mossbauer (SM) source, taking advantage of the fully polarised state of the source to simplify the analysis. Mean in-plane canting angles of order 12° were found for both sets of ribbons in an applied field of 1.1 T, in keeping with earlier results in smaller fields. The spectra were found to be dependent on the direction of the applied field in the ribbon plane, indicating structural anisotropy in all the samples, consistent with the presence of residual casting strains.
Journal of Physics: Condensed Matter | 1993
Yu. V. Shvyd'ko; S. L. Popov; G. V. Smirnov
The re-emission of gamma -quanta in the forward direction by an ensemble of excited nuclei after abruptly changing the energy of the nuclear excitation is studied. A sublevel of the 14.4 keV excited state with a definite spin projection of 57Fe nuclei in a magnetic 57FeBO3 crystal is selectively populated. The abrupt change of the energy of the excited nuclear state is achieved by fast (<or=5 ns) reversal of the hyperfine (HF) magnetic field direction at the nuclei. The nuclear target was a black absorber prior to HF field reversal. A short (about 10 ns) intense flash followed by beats of gamma -radiation intensity is detected with some delay after reversal. The delay of the flash and the beat period depend on the HF nuclear transition excited. The duration of the flash depends on the effective thickness of the nuclear target. The theory developed interprets the time evolution of the re-emission as a result of the interference of two main spectral components of gamma -radiation. The first one has the original frequency, which represents the primary radiation. The second one has a shifted frequency, which represents radiation coherently re-emitted in the forward direction from the nuclear sublevel with energy changed by the HF field reversal. The observations reveal the feasibility of inelastic coherent gamma -resonance scattering and demonstrate the enhancement of the radiative channel in the coherent re-emission of gamma -radiation in the forward direction.