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The formation of high-pressure oxyhydroxide phases spanned by the components AlOOH-FeOOH-MgSiO2(OH)2 in experiments suggests their capability to retain hydrogen in Earth's lower mantle. Understanding the vibrational properties of high-pressure phases provides the basis for assessing their thermal properties, which are required to compute phase diagrams and physical properties. Vibrational properties can be highly anisotropic, in particular for materials with crystal structures of low symmetry that contain directed structural groups or components. We used nuclear resonant inelastic X-ray scattering (NRIXS) to probe lattice vibrations that involve motions of 57Fe atoms in δ-(Al0.87Fe0.13)OOH single crystals. From the recorded single-crystal NRIXS spectra, we calculated projections of the partial phonon density of states along different crystallographic directions. To describe the anisotropy of central vibrational properties, we define and derive tensors for the partial phonon density of states, the Lamb-Mössbauer factor, the mean kinetic energy per vibrational mode, and the mean force constant of 57Fe atoms. We further show how the anisotropy of the Lamb-Mössbauer factor can be translated into anisotropic displacement parameters for 57Fe atoms and relate our findings on vibrational anisotropy to the crystal structure of δ-(Al,Fe)OOH. As a potential application of single-crystal NRIXS at high pressures, we discuss the evaluation of anisotropic thermal stresses in the context of elastic geobarometry for mineral inclusions. Our results on single crystals of δ-(Al,Fe)OOH demonstrate the sensitivity of NRIXS to vibrational anisotropy and provide an in-depth description of the vibrational behavior of Fe3C cations in a crystal structure that may motivate future applications of NRIXS to study anisotropic vibrational properties of minerals. [ABSTRACT FROM AUTHOR]

Abstract The role of active-interrogation systems for nuclear security is to detect the presence of special nuclear material inside an object by observing the radiation emitted by that object when it has been exposed to known sources of external radiation. Because of the cost, complexity, and the need to avoid irradiating occupants, active-interrogation systems are intended for cargo applications where shielding can prevent detection by passive radiation detection systems. To ensure that active-interrogation systems for detection of special nuclear material are designed and tested to a consistent level of performance, technical standards are needed for evaluating such systems. This paper addresses the testing standards needed for active-interrogation systems to detect high atomic number materials, fissionable materials, and specific special nuclear materials. Because the use of special nuclear material for a testing standard is not practical, this work focuses on the determination of materials that could be used as surrogates in that they provide a similar response as targets of special nuclear materials. The results of this paper, determined through analytic calculations and radiation transport modeling, are based upon scenarios constructed and applied to specific active-interrogation modalities. [ABSTRACT FROM AUTHOR]

Sulfur contamination has been a serious issue in oil industry so that desulfurization becomes a vital step in oil refinery to offer sulfur free products. The success of desulfurization requires disproportionation of sulfur‐containing molecules to form sulfur‐catenated compounds and further remove sulfur (S8). The reaction of ethyl acetate (EtOAc) with the gaseous components of products from the thermal decomposition of thiourea (condition 1) and the direct decomposition of thiourea in dimethyl sulfoxide (condition 2) provide two series of sulfur‐catenated molecules that have been characterized by gas chromatography‐mass spectrometry and partially by nuclear resonance spectroscopy with the help of ab initio calculation. This new method of in‐situ generating alkyl polysulfides might be applied to remove sulfur from the sulfur‐containing molecules in oil refining process to diminish the sulfur contents in oil products. Thiourea undergoes thermal decomposition to form different compounds depending on the decomposition temperature. The resulting products can further react with ethyl acetate or dimethyl sulfoxide to yield a series of organic sulfur‐clusters, either in cyclic or linear forms. [ABSTRACT FROM AUTHOR]

Hydrogen bonds (H‐bonds) have been shown to modulate the chemical reactivities of iron centers in iron‐containing dioxygen‐activating enzymes and model complexes. However, few examples are available that investigate how systematic changes in intramolecular H‐bonds within the secondary coordination sphere influence specific properties of iron intermediates, such as iron‐oxido/hydroxido species. Here, we used 57Fe nuclear resonance vibrational spectroscopy (NRVS) to probe the Fe‐O/OH vibrations in a series of FeIII‐hydroxido and FeIV/III‐oxido complexes with varying H‐bonding networks but having similar trigonal bipyramidal primary coordination spheres. The data show that even subtle changes in the H‐bonds to the Fe‐O/OH units result in significant changes in their vibrational frequencies, thus demonstrating the utility of NRVS in studying the effect of the secondary coordination sphere to the reactivities of iron complexes. [ABSTRACT FROM AUTHOR]

Abstract Nuclear resonance fluorescence (NRF) is a photonuclear interaction that enables highly isotope-specific measurements in both pure and applied physics scenarios. High-accuracy design and analysis of NRF measurements in complex geometries is aided by Monte Carlo simulations of photon physics and transport, motivating Jordan and Warren (2007) to develop the G4NRF codebase for NRF simulation in Geant4. In this work, we enhance the physics accuracy of the G4NRF code and perform improved benchmarking simulations. The NRF cross section calculation in G4NRF, previously a Gaussian approximation, has been replaced with a full numerical integration for improved accuracy in thick-target scenarios. A high-accuracy semi-analytical model of expected NRF count rates in a typical NRF measurement is then constructed and compared against G4NRF simulations for both simple homogeneous and more complex heterogeneous geometries. Agreement between rates predicted by the semi-analytical model and G4NRF simulation is found at a level of ∼ 1 % in simple test cases and ∼ 3 % in more realistic scenarios, improving upon the ∼ 20 % level of the initial benchmarking study and establishing a highly-accurate NRF framework for Geant4. [ABSTRACT FROM AUTHOR]

Highlights • The bulk strength was determined of FeNi alloys at high pressures. • At inner core conditions, an Fe 94.5 Ni 5.5 alloy would have a 125% greater strength than Fe. • Dislocation creep is likely the dominant mechanism in the Earth’s inner core. Abstract We investigated the effect of nickel on the strength of iron-nickel (FeNi) alloys at high pressure. Using radial X-ray diffraction coupled with literature results from nuclear resonance inelastic X-ray scattering measurements we determined the bulk strength of two FeNi alloys (Fe 0.88 Ni 0.12 and Fe 0.8 Ni 0.2) at high pressures up to 70 GPa. When extrapolated to Earth’s inner core conditions, the strength of these FeNi alloys is found to increase relative to pure Fe. For the likely composition and conditions of the inner core, we estimate that an FeNi alloy with ∼5.5 wt% Ni would have a strength that is ∼125% greater than estimates for pure Fe. As shear strength is a measure of a material’s resistance to flow, our results have implications for understanding the deformation processes inside planetary interiors and support dislocation creep as the dominant mechanism in the Earth’s inner core. [ABSTRACT FROM AUTHOR]

The synchrotron radiation technique of nuclear resonant inelastic X‐ray scattering (NRIXS), also known as nuclear resonance vibrational spectroscopy or nuclear inelastic scattering, provides a wealth of information on the vibrational properties of solids. It has found applications in studies of lattice dynamics and elasticity, superconductivity, heme biochemistry, seismology, isotope geochemistry and many other fields. It involves probing the vibrational modes of solids by using the nuclear resonance of Mössbauer isotopes such as 57Fe, 83Kr, 119Sn, 151Eu and 161Dy. After data reduction, it provides the partial phonon density of states of the Mössbauer isotope that is investigated, as well as many other derived quantities such as the mean force constant of the chemical bonds and the Debye velocity. The data reduction is, however, not straightforward and involves removal of the elastic peak, normalization and Fourier–Log transformation. Furthermore, some of the quantities derived are highly sensitive to details in the baseline correction. A software package and several novel procedures to streamline and hopefully improve the reduction of the NRIXS data generated at sector 3ID of the Advanced Photon Source have been developed. The graphical user interface software is named SciPhon and runs as a Mathematica package. It is easily portable to other platforms and can be easily adapted for reducing data generated at other beamlines. Several tests and comparisons are presented that demonstrate the usefulness of this software, whose results have already been used in several publications. Here, the SciPhon software is used to reduce Kr, Sn, Eu and Dy NRIXS data, and potential implications for interpreting natural isotopic variations in those systems are discussed. [ABSTRACT FROM AUTHOR]

A resonance structure of the charge-exchange strength function S(E) and its effect on the neutrino-capture cross sections for the isotopes 71Ga, 98Mo, and 127I are studied within the self-consistent theory of finite Fermi systems. The calculation of the strength function S(E) takes into account Gamow-Teller, analog, and so-called lower lying pygmy resonances. The neutrino-capture cross sections σ(E) for the above three isotopes are calculated with allowance for the resonance structure of the strength function S(E), and the effect of each resonance on the energy dependence σ(E) is analyzed. It is found that all charge-exchange resonances in the strength function S(E) should be taken into account in calculating the neutrino-capture cross section σ(E) for the isotopes 71Ga, 98Mo, and 127I. The disregard of even highlying resonances leads to a substantial underestimation of the cross section σ(E), and this may affect the interpretation of respective experimental data. [ABSTRACT FROM AUTHOR]

Abstract: High‐spin iron species with bridging hydrides have been detected in species trapped during nitrogenase catalysis, but there are few general methods of evaluating Fe−H bonds in high‐spin multinuclear iron systems. An 57Fe nuclear resonance vibrational spectroscopy (NRVS) study on an Fe(μ‐H)2Fe model complex reveals Fe−H stretching vibrations for bridging hydrides at frequencies greater than 1200 cm−1. These isotope‐sensitive vibrational bands are not evident in infrared (IR) spectra, showing the power of NRVS for identifying hydrides in this high‐spin iron system. Complementary density functional theory (DFT) calculations elucidate the normal modes of the rhomboidal iron hydride core. [ABSTRACT FROM AUTHOR]

In this paper, we have discussed the non-relativistic and relativistic treatment of the recoil energy of photon due to the nuclear transition and atomic transition and calculated the total energy of the recoil event for atomic and nuclear transition which concluded that the relativistic recoil energy of photon due to nuclear transition is 105 times greater than that of atomic transition. [ABSTRACT FROM AUTHOR]

In this communication, we identify some thermal-plasma assisted synthesis techniques for the alternative production of fusion relevant tungsten dust particles in bulk amounts, to allow for the statistically meaningful study of their hydrogen absorption properties. Fast, single step synthesis of fine particles in the α-tungsten phase was demonstrated, using a high heat flux device for sizes in the micrometer region and an experimental nanoparticle reactor for dust with nanometer sizes. Production of both equilibrium polyhedral and nonequilibrium spherulitic crystal shapes was demonstrated, dust morphologies similar to which were identified before in existing tokamaks and divertor simulator systems. Their hydrogen retention characteristics were measured by the Nuclear Resonance Reaction Analysis technique, which was found to be orders of magnitude higher compared to the same metal in the bulk form. The mesoporous crystals generated during high power, high pressure synthesis conditions were assumed to be responsible for the unusually high gas retention of the nanoparticle sample. It was concluded that non-equilibrium tungsten dust morphologies would be dominant in the high power fusion machines in the future, which may aggravate the hydrogen isotope retention issues further. [ABSTRACT FROM AUTHOR]

A novel sample environment enabling optical pump - nuclear resonance probe experiments has been installed at the beamline P01, Petra III, DESY Hamburg. This set-up has been used to investigate optically induced spin state changes of spin crossover (SCO) complexes by nuclear resonant scattering immediately after excitation by an optical laser pulse. Here, we report the technical details as well as first results of the experiments performed at 290 K and 80 K on the SCO complexes [Fe (NHtrz)]Cl and [Fe(PM-BiA)(NCS)], respectively. The Fe-enriched SCO complexes were excited by a 531 nm laser with a pulse length < 100 ps. Evaluation of the nuclear forward scattering data clearly indicate the presence of high spin (HS) states when the complexes are excited by laser pulses and a pure low spin (LS) state in the absence of any laser pulse. Furthermore, the dependence of the optically excited HS-fraction has been determined as a function of the average optical power. [ABSTRACT FROM AUTHOR]

The present work aims at contributing to the field of Ion Beam Analysis by providing a set of standard, high-accuracy nuclear resonance reaction data points to be used for accelerator energy calibration up to 4.6 MeV, more specifically with the use of the 27 Al(p,γ), 13 C(p,γ), 12 C(p,p 0 ) and 32 S(p,p′γ) resonant reactions, as a result of a comprehensive investigation in two different laboratories. The use of resonances at higher energies, namely up to 6 MeV, is also discussed. The measurements have been performed at two different electrostatic accelerators, namely at the 5.5 MV HV TN-11 of NCSR “Demokritos”, Greece, and at the 5 MV 15SDH-2 Pelletron Tandem accelerator at Uppsala University in Uppsala, Sweden. Common points were used to normalize and validate the data. The possible use of the 16 O(p,p 0 ) resonance at 3.47 MeV is also discussed and analyzed. [ABSTRACT FROM AUTHOR]

A portable double-sided pulsed laser heating system for diamond anvil cells has been developed that is able to stably produce laser pulses as short as a few microseconds with repetition frequencies up to 100 kHz. In situ temperature determination is possible by collecting and fitting the thermal radiation spectrum for a specific wavelength range (particularly, between 650 nm and 850 nm) to the Planck radiation function. Surface temperature information can also be time-resolved by using a gated detector that is synchronized with the laser pulse modulation and space-resolved with the implementation of a multi-point thermal radiation collection technique. The system can be easily coupled with equipment at synchrotron facilities, particularly for nuclear resonance spectroscopy experiments. Examples of applications include investigations of high-pressure high-temperature behavior of iron oxides, both in house and at the European Synchrotron Radiation Facility using the synchrotron Mossbauer source and nuclear inelastic scattering. [ABSTRACT FROM AUTHOR]

Spectroscopy of nuclear resonances offers a wide range of applications due to the remarkable energy resolution afforded by their narrow linewidths. However, progress toward higher resolution is inhibited at modern x-ray sources because they deliver only a tiny fraction of the photons on resonance, with the remainder contributing to an off-resonant background. We devised an experimental setup that uses the fast mechanical motion of a resonant target to manipulate the spectrum of a given x-ray pulse and to redistribute off-resonant spectral intensity onto the resonance. As a consequence, the resonant pulse brilliance is increased while the off-resonant background is reduced. Because our method is compatible with existing and upcoming pulsed x-ray sources, we anticipate that this approach will find applications that require ultranarrow x-ray resonances. [ABSTRACT FROM AUTHOR]

New results, additional techniques and know-how acquired, developed and employed in a recent HC-1898 experiment at the Nuclear Resonance Beamline ID18 of ESRF are presented, in the quest to explore the acceleration effect on time dilation. Using the specially modified Synchrotron Mössbauer Source and KB-optics together with a rotating single-line semicircular Mössbauer absorber on the rim of a specially designed rotating disk, the aim was to measure the relative spectral shift between the spectra of two states when the acceleration of the absorber is anti-parallel and parallel to the source. A control system was used for the first time and a method to quantify the effects of non-random vibrations on the spectral shift was developed. For several runs where the effect of these vibrations was negligible, a stable statistically significant non-zero relative shift was observed. This suggests the influence of acceleration on time. [ABSTRACT FROM AUTHOR]

Iron-based metallic glasses (MGs) are typical representatives of disordered alloys. They exhibit amorphous structure that is lacking any long-range order. Appropriate chemical composition of MGs ensures soft magnetic properties suitable for variety of practical applications. Because the beneficial magnetic properties are closely related to structural features of MGs it is inevitable to understand the ways how and under which conditions is their original structure modified. Notably elevated temperature can induce formation of crystallites that alter the desired magnetic parameters. Here, we demonstrate the use of 57Fe Mössbauer spectrometry and nuclear forward scattering of synchrotron radiation for the study of structural transformations in (Fe2.85Co1)77Mo8Cu1B14 MG which was chosen as an example. These techniques are based upon nuclear resonances that can scan evolution of hyperfine interactions acting upon nuclear levels of a stable 57Fe isotope. Because iron is typical constituent element of MGs, any deviations from original structural arrangement including modifications of the chemical surrounding can be studied. [ABSTRACT FROM AUTHOR]

[FeFe]-hydrogenases catalyze the reversible reduction of protons to molecular hydrogen with extremely high efficiency. The active site (-œH-cluster') consists of a [4Fe-4S]H cluster linked through a bridging cysteine to a [2Fe]H subsite coordinated by CN- and CO ligands featuring a dithiol-amine moiety that serves as proton shuttle between the protein proton channel and the catalytic distal iron site (Fed). Although there is broad consensus that an iron-bound terminal hydride species must occur in the catalytic mechanism, such a species has never been directly observed experimentally. Here, we present FTIR and nuclear resonance vibrational spectroscopy (NRVS) experiments in conjunction with density functional theory (DFT) calculations on an [FeFe]-hydrogenase variant lacking the amine proton shuttle which is stabilizing a putative hydride state. The NRVS spectra unequivocally show the bending modes of the terminal Fe-H species fully consistent with widely accepted models of the catalytic cycle. [ABSTRACT FROM AUTHOR]

A review is given about the long-standing search for dibaryons, i.e. six-quark objects, from the early days until present, when the first dibaryon resonance has been established, which has the potential of constituting a compact six-quark object. [ABSTRACT FROM AUTHOR]

A numerical solution has been obtained for a two-level atomic system interacting with a 101-component polychromatic field. The analytical method of recurrence relations has confirmed the numerical calculations. The resonance in the polarization spectrum follows the transition frequency. [ABSTRACT FROM AUTHOR]

A Mössbauer diffractometer has been developed by using Fe nuclear resonant scattering apparatus at SPring-8 BL11XU in order to obtain a crystal-site-selective Mössbauer spectrum. A 휃-2 휃 goniometer was newly installed between the nuclear monochromator and a detector. From a single crystal Fe O mounted on the goniometer, the 111, 222, and 220 reflected γ-rays were used to collect the diffraction spectra at room temperature. The intensity ratio of the two subspectra, corresponding to A- and B-site Fe ions, changes notably according to the reflection index. The diffraction spectrum is composed of a major absorption spectrum and a minor emission spectrum. The former is given by the γ-ray due to the electron scattering and nuclear absorption, whereas the latter is given by the γ-ray due to the nuclear resonant scattering. Interference effects between these two γ-rays are also seen as line broadenings, asymmetric line shapes, and slope of the base lines. These features can be successfully expressed by a Fano function. We consider that the emission spectrum due to the nuclear resonant scattering represents crystal-site-selective Mössbauer spectrum. [ABSTRACT FROM AUTHOR]

We establish the equivalence of the various techniques for measuring B(E2) values using a statistical analysis. Data used in this work come from the recent compilation by B. Pritychenko et al. (2016) [5] . We consider only those nuclei for which the B(E2) values were measured by at least two different methods, with each method being independently performed at least twice. Our results indicate that most prevalent methods of measuring B(E2) values are equivalent, with some weak evidence that Doppler-shift attenuation method (DSAM) measurements may differ from Coulomb excitation (CE) and nuclear resonance fluorescence (NRF) measurements. However, such an evidence appears to arise from discrepant DSAM measurements of the lifetimes for 60 Ni and some Sn nuclei rather than a systematic deviation in the method itself. [ABSTRACT FROM AUTHOR]

The superconformal algebraic approach to hadronic physics is used to construct a semiclassical effective theory for nucleons which incorporates essential nonperturbative dynamical features, such as the emergence of a confining scale and the Regge resonance spectrum. Relativistic bound-state equations for nucleons follow from the extension of superconformal quantum mechanics to the light front and its holographic embedding in a higher dimensional gravity theory. Superconformal algebra has been used elsewhere to describe the connections between the light mesons and baryons, but in the present context it relates the fermion positive and negative chirality states and uniquely determines the confinement potential of nucleons. The holographic mapping of multi-quark bound states also leads to a light-front cluster decomposition of form factors for an arbitrary number of constituents. The remarkable analytical structure which follows incorporates the correct scaling behavior at high photon virtualities and also vector dominance at low energies. [ABSTRACT FROM AUTHOR]

A method is proposed for measuring the sensitivity of nuclear resonance magnetometers in flowing liquids for use in detecting magnetic field frequencies of 0.5-600 MHz. This method is based on mathematical analysis of experimental data obtained by measuring the slope of the nutation line at the point where the inverted nuclear magnetic resonance signal passes through zero. [ABSTRACT FROM AUTHOR]

The vibrational spectrum of a six-coordinate nitrosyl iron porphyrinate, monoclinic [Fe(T pFPP)(1-MeIm)(NO)] (T pFPP=tetra- para-fluorophenylporphyrin; 1-MeIm=1-methylimidazole), has been studied by oriented single-crystal nuclear resonance vibrational spectroscopy (NRVS). The crystal was oriented to give spectra perpendicular to the porphyrin plane and two in-plane spectra perpendicular or parallel to the projection of the FeNO plane. These enable assignment of the FeNO bending and stretching modes. The measurements reveal that the two in-plane spectra have substantial differences that result from the strongly bonded axial NO ligand. The direction of the in-plane iron motion is found to be largely parallel and perpendicular to the projection of the bent FeNO on the porphyrin plane. The out-of-plane Fe-N-O stretching and bending modes are strongly mixed with each other, as well as with porphyrin ligand modes. The stretch is mixed with v50 as was also observed for dioxygen complexes. The frequency of the assigned stretching mode of eight Fe-X-O (X=N, C, and O) complexes is correlated with the Fe−XO bond lengths. The nature of highest frequency band at ≈560 cm−1 has also been examined in two additional new derivatives. Previously assigned as the Fe−NO stretch (by resonance Raman), it is better described as the bend, as the motion of the central nitrogen atom of the FeNO group is very large. There is significant mixing of this mode. The results emphasize the importance of mode mixing; the extent of mixing must be related to the peripheral phenyl substituents. [ABSTRACT FROM AUTHOR]