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Ruby, S. L.; Bolef, D. I.

doi:10.1103/physrevlett.5.5

Cited by 137 publications

(33 citation statements)

References 3 publications

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“…The incoherent model was proposed [26][27][28][29][30] to explain the discrepancy between the coherent model and the experiment. It is based on the Abragam model [35] suggesting that the motion of individual nucleus in the absorber along the propagation direction z of γ photon can be described as a z (t) = a c cos(Ωt + ψ) + a s sin(Ωt + ψ), where a c and a s are the amplitudes of in phase and out of phase oscillations [27].…”

Section: B Incoherent Modelmentioning

confidence: 99%

“…Usually these absorbers are glued on the surface of the transducer, fed by the oscillating voltage. The transducers, made from piezo-crystal (for example, quartz) [23,24,[26][27][28][29][30][31][32][33][34] or piezo-polymerfilm (for example, a polyvinylidene fluoride -PVDF), also produce different spectra since the conversion factor of the PVDF drive is more than ten times larger than that of quartz [38]. Meanwhile, the Rayleigh distribution has only one parameter, which is a variance of the displacement amplitude a 2 , specifying also the values m 2 and m. However, in general the distribution of amplitudes and phases of the nuclear vibrations should depend on the construction of the absorber-transducer.…”

Section: The Arguments For a Revision Of The Incoherent Modelmentioning

confidence: 99%

“…Mössbauer sidebands, produced from a single parent line by absorber vibration, were observed in many different samples [23,24,[26][27][28][29][30][31][32][33][34]. However, the intensity of the sidebands has not been yet satisfactory explained [30][31][32].…”

Section: Introductionmentioning

confidence: 99%

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Application of the Mössbauer effect to the study of subnanometer harmonic displacements in thin solids

Shakhmuratov

Vagizov

2017

Phys. Rev. B

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We measure subnanometer displacements of thin samples vibrated by piezotransducer. Samples contain 57 Fe nuclei, which are exposed to 14.4 keV γ-radiation. Vibration produces sidebands from a single absorption line of the sample. The sideband intensities depend on the vibration amplitude and its distribution along the sample. We developed a model of this distribution, which adequately describes the spectra of powder and stainless steel (SS) absorbers. We propose to filter γ-radiation through a small round hole in the lead mask, placed before the absorber. In this case only a small spot of the vibrated absorber is observed. We found for SS foil that nuclei, exposed to γ-radiation in this small spot, vibrate with almost the same amplitudes whose difference does not exceed a few picometers within the irradiated area.

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Section: B Incoherent Modelmentioning

confidence: 99%

Section: The Arguments For a Revision Of The Incoherent Modelmentioning

confidence: 99%

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Application of the Mössbauer effect to the study of subnanometer harmonic displacements in thin solids

Shakhmuratov

Vagizov

2017

Phys. Rev. B

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“…Additional support for the claims that the Mössbauer spectra are inhomogeneous, composed of narrow lines, and that external fluctuations produce these narrow sidebands comes from experiments where the fluctuations are produced by piezoelectric crystals (35,36).…”

Section: Elmmentioning

confidence: 99%

A wave-mechanical model of incoherent quasielastic scattering in complex systems

Frauenfelder

Fenimore

Young

2014

Proc. Natl. Acad. Sci. U.S.A.

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Quasielastic incoherent neutron scattering (QENS) is an important tool for the exploration of the dynamics of complex systems such as biomolecules, liquids, and glasses. The dynamics is reflected in the energy spectra of the scattered neutrons. Conventionally these spectra are decomposed into a narrow elastic line and a broad quasielastic band. The band is interpreted as being caused by Doppler broadening due to spatial motion of the target molecules. We propose a quantum-mechanical model in which there is no separate elastic line. The quasielastic band is composed of sharp lines with twice the natural line width, shifted from the center by a random walk of the protein in the free-energy landscape of the target molecule. The walk is driven by vibrations and by external fluctuations. We first explore the model with the Mössbauer effect. In the subsequent application to QENS we treat the incoming neutron as a de Broglie wave packet. While the wave packet passes the protons in the protein and the hydration shell it exchanges energy with the protein during the passage time of about 100 ns. The energy exchange broadens the ensemble spectrum. Because the exchange involves the free-energy landscape of the protein, the QENS not only provides insight into the protein dynamics, but it may also illuminate the free-energy landscape of the protein-solvent system. quasielastic neutron scattering | neutron wave packet | protein free-energy landscape Q uasielastic effects are a key to understanding the dynamics of complex systems, from water to proteins (1, 2). A novice trying to understand quasielastic incoherent neutron scattering (QENS) is easily mystified. "Quasielastic" is usually taken to mean broadening of the elastic line due to spatial diffusion of the scattering particle. This definition is vague. We introduce a model that permits an unambiguous definition. It describes the QENS of proteins as involving a random walk in the free-energy landscape (FEL), driven by external fluctuations and by thermal vibrations. During the walk, the neutrons exchange energy with the protein, thus broadening the energy spectrum.In QENS the energy spectrum I(ΔE) of the scattered neutrons is measured as a function of the energy transfer ΔE relative to the energy of the elastic line at ΔE = 0. At present the QENS spectra are separated into a narrow elastic peak and a broad quasielastic band shown schematically in Fig. 1A. The band is taken to consist of broad Lorentzians with width Γ h centered at ΔE = 0 as sketched in Fig. 1B. The broadening is attributed to spatial motion of the target atoms, for instance by continuous diffusion, by jumps from one lattice site to another, or by conformational changes in proteins. The motions lead to different width Γ h for different proteins. We call this model SMM, for "spatial motion model," and discuss it in more detail later. We have introduced a radically different model, ELM, for "energy landscape model" (3). In the ELM, there is no separate elastic line pinned to the center. The entire spectrum is ...

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“…The broad spectrum is therefore inhomogeneous, composed of lines with narrow widths. This explanation has been proven with the Mössbauer effect (3,5) and for neutron scattering (6) when the samples experience driven vibrations.…”

mentioning

confidence: 90%

The role of momentum transfer during incoherent neutron scattering is explained by the energy landscape model

Frauenfelder

Young

Fenimore

2017

Proc. Natl. Acad. Sci. U.S.A.

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We recently introduced a model of incoherent quasielastic neutron scattering (QENS) that treats the neutrons as wave packets of finite length and the protein as a random walker in the free energy landscape. We call the model ELM for "energy landscape model." In ELM, the interaction of the wave packet with a proton in a protein provides the dynamic information. During the scattering event, the momentum Q(t) is transferred by the wave packet to the struck proton and its moiety, exerting the force F(t) = dQ(t)/dt. The resultant energy E is stored elastically and returned to the neutron as it exits. The energy is given by E = k B (T 0 + χQ), where T 0 is the ambient temperature and χ (≈ 91 KÅ) is a new elastobaric coefficient. Experiments yield the scattering intensity (dynamic structure factor) S(Q; T) as a function of Q and T. To test our model, we use published data on proteins where only thermal vibrations are active. ELM competes with the currently accepted theory, here called the spatial motion model (SMM), which explains S(Q, T) by motions in real space. ELM is superior to SMM: It can explain the experimental angular and temperature dependence, whereas SMM cannot do so.QENS | de Broglie neutron wave packet | pressure-temperature equivalence | transient energy transfer I ncoherent quasielastic neutron scattering (QENS) is used to study, for instance, the dynamics of complex systems (1, 2). In these experiments, the scattering intensity S (Q, ω, T ) is measured as function of temperature T , momentum transfer Q, and energy transfer ω. "Incoherent" essentially means that the neutron scatters from only one proton, and thus interference from different protons does not contribute. To extract the information from the data, a model is needed. The currently accepted model, used for > 50 y, assumes that the observed effects are due to spatial motions. We call it the spatial motion model (SMM). We recently introduced a model in which S (Q, ω, T ) is based on motions in the conformational free energy landscape (FEL) (3, 4). We call the model ELM, for energy landscape model. ELM assumes that the effects observed in QENS are predominantly due to changes in the population of the FEL. ELM as introduced in ref. 4 explained the neutron scattering from proteins, but left the role of the momentum transfer Q in limbo. The Q dependence is noteworthy because, although the physics of n-p scattering at low energies is s-wave (isotropic), the observed scattering from proteins is Q-dependent (see Fig. 3A), meaning anisotropic. We have now found that Q plays an important role: It creates an inhomogeneity in the target during the passage of the neutron.Consider a neutron with wave vector q that hits a proton in a protein. S (Q, ω, T ) is measured as a function of the temperature T at different scattering angles, characterized by their wave vectors q . The wave vectors q and q determine the transferred wave vector, Q = q − q. Q is related to the momentum by P = Q. E = ω is the energy change of the neutron when it has completed its scatter...

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Acoustically ModulatedγRays FromFe57

Cited by 137 publications

References 3 publications

Application of the Mössbauer effect to the study of subnanometer harmonic displacements in thin solids

Application of the Mössbauer effect to the study of subnanometer harmonic displacements in thin solids

A wave-mechanical model of incoherent quasielastic scattering in complex systems

The role of momentum transfer during incoherent neutron scattering is explained by the energy landscape model

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