Inelastic Scattering Research Articles

Improving the sensitivity of fast neutron inelastic scatter analysis to iron using associated particle collimation

The purpose of this study is twofold; first, a prompt gamma-ray neutron activation analysis (PGNAA) system will be constructed and employed in order to find the approximate sensitivity to elemental iron upon spectroscopic analysis. Concurrently, a Monte Carlo (MC) simulation model of the same PGNAA system will be defined such that the neutron source and resulting gamma-ray emissions are temporally collimated using the neutron associated particle (AP) technique. The experimental and simulated gamma-ray spectra may then be compared – taking into account the technological parameters and physical limitations of the PGNAA system – to determine how the sensitivity of the system may be improved due to photon signal discrimination inherent to the application of AP timing.

Multidimensional Bin-Width Optimization for Histogram and Its Application to Four-Dimensional Neutron Inelastic Scattering Data

We propose a method for optimizing bin widths for multidimensional histograms. The optimization criterion is based on a cost function representing the tradeoff between the reduction of stochastic f...

Vertex corrections to the dc conductivity in anisotropic multiband systems

For an isotropic single-band system, it is well known that the semiclassical Boltzmann transport theory within the relaxation time approximation and the Kubo formula with the vertex corrections provide the same result with the $(1-\cos\theta)$ factor in the inverse transport relaxation time. In anisotropic multiband systems, the semiclassical Boltzmann transport equation is generalized to coupled integral equations relating transport relaxation times at different angles in different bands. Using the Kubo formula, we study the vertex corrections to the dc conductivity in anisotropic multiband systems and derive the relation satisfied by the transport relaxation time for both elastic and inelastic scatterings, verifying that the result is consistent with the semiclassical approach.

Quantum Behavior of Spin-Orbit Inelastic Scattering of C-Atoms by D2 at Low Energy.

Fine-structure populations and collision–induced energy transfer in atoms are of interest for many fields, from combustion to astrophysics. In particular, neutral carbon atoms are known to play a role in interstellar media, either as probes of physical conditions (ground state 3Pj spin-orbit populations), or as cooling agent (collisional excitation followed by radiative decay). This work aims at investigating the spin-orbit excitation of atomic carbon in its ground electronic state due to collisions with molecular deuterium, an isotopic variant of H2, the most abundant molecule in the interstellar medium. Spin-orbit excitations of C(3Pj) by H2 or D2 are governed by non-adiabatic and spin-orbit couplings, which make the theoretical treatment challenging, since the Born-Oppenheimer approximation no longer holds. Inelastic collisional cross-sections were determined for the C(3P0) + D2 → C(3Pj) + D2 (with j = 1 and 2) excitation process. Experimental data were acquired in a crossed beam experiment at low collision energies, down to the excitation thresholds (at 16.42 and 43.41 cm−1, respectively). C-atoms were produced mainly in their ground spin-orbit state, 3P0, by dissociation of CO in a dielectric discharge through an Even-Lavie pulsed valve. The C-atom beam was crossed with a D2 beam from a second valve. The state-to-state cross-sections were derived from the C(3Pj) (j = 1 or 2) signal measured as a function of the beam crossing angle, i.e., as a function of the collision energy. The results show different quantum behaviors for excitation to C(3P1) or C(3P2) when C(3P0) collides with ortho-D2 or normal-D2. These experimental results are analyzed and discussed in the light of highly accurate quantum calculations. A good agreement between experimental and theoretical results is found. The present data are compared with those obtained for the C-He and C-H2 collisional systems to get new insights into the dynamics of collision induced spin-orbit excitation/relaxation of atomic carbon.

Determination of the scattering cross section of calcium using the VESUVIO spectrometer

Abstract With the aim to study the bound-atom neutron scattering cross section of natural calcium we measured the total cross sections of calcium carbonate and calcium oxide for the energy range between 10−3 and 100 eV, at the VESUVIO spectrometer (Rutherford Appleton Laboratory, UK), where we carried out simultaneous transmission and Deep Inelastic Neutron Scattering measurements. We present a method that allows us to determine in situ the amount of water present in the samples, which are both of hygroscopic nature. By employing it, we were able to subtract the contribution of hydrogen from the total cross section, as well as that of the other atoms present in the sample whose amount was known by their stoichiometry, what allowed us to determine the calcium contribution. The process of quantifying the amount of water involves the analysis of the scattered neutrons and multiple scattering corrections. In order to perform this last correction, we made a prior study of the dynamics of the system by means of the Density Functional Theory technique, along with measurements of the vibrational spectra at the TOSCA spectrometer (Rutherford Appleton Laboratory, UK). The value determined for the bound-atom scattering cross section of calcium was 4.27 ± 0.04 barns.

New Insights about CuO Nanoparticles from Inelastic Neutron Scattering.

Inelastic Neutron Scattering (INS) spectroscopy has provided a unique insight into the magnetodymanics of nanoscale copper (II) oxide (CuO). We present evidence for the propagation of magnons in the directions of the ordering vectors of both the commensurate and helically modulated incommensurate antiferromagnetic phases of CuO. The temperature dependency of the magnon spin-wave intensity (in the accessible energy-range of the experiment) conforms to the Bose population of states at low temperatures (T ≤ 100 K), as expected for bosons, then intensity significantly increases, with maximum at about 225 K (close to TN), and decreases at higher temperatures. The obtained results can be related to gradual softening of the dispersion curves of magnon spin-waves and decreasing the spin gap with temperature approaching TN on heating, and slow dissipation of the short-range dynamic spin correlations at higher temperatures. However, the intensity of the magnon signal was found to be particle size dependent, and increases with decreasing particle size. This “reverse size effect” is believed to be related to either creation of single-domain particles at the nanoscale, or “superferromagnetism effect” and the formation of collective particle states.

Optical gain of inelastic exciton-exciton scattering in CdS nanowires

We have performed a variable stripe length method at 5 K to measure the optical gain of CdS nanowires. When the excited carrier density is lower than the Mott density, we found that various inelastic scatterings of excitons and LO-phonons are involved. As a consequence of inelastic exciton-exciton scattering, the excitons scattered down to the low polariton branch cause P-emission lasing, and the excited excitons also result in a population inversion through intra-relaxation. When LO-phonon scatterings are involved, a broad optical gain spectrum is observed resulting from exciton-LO and P-LO scatterings.

Probing Magnetic Excitations in CoII Single-Molecule Magnets by Inelastic Neutron Scattering.

Co(acac)2(H2O)2 (1, acac = acetylacetonate), a transition metal complex ( ), displays field-induced slow magnetic relaxation as a single-molecule magnet. For 1 and its isotopologues Co(acac)2(D2O)2 (1-d 4 ) and Co(acac-d 7)2(D2O)2 (1-d 18 ) in approximately symmetry, zero-field splitting of the ground electronic state leads to two Kramers doublets (KDs): lower energy and higher energy states. This work employs inelastic neutron scattering (INS), a unique method to probe magnetic transitions, to probe different magnetic excitations in 1-d 4 and 1-d 18 . Direct-geometry, time-of-flight Disk-Chopper Spectrometer (DCS), with applied magnetic fields up to 10 T, has been used to study the intra-KD transition as a result of Zeeman splitting, , in 1-d 18 . This is a rare study of the excitation in transition metal complexes by INS. Indirect-geometry INS spectrometer VISION has been used to probe the inter-KD, ZFS transition, in both 1-d 4 and 1-d 18 , by variable-temperature (VT) properties of this excitation. The INS spectra measured on VISION also give phonon features of the complexes that are well described by periodic DFT phonon calculations.

Proton induced differential cross sections on 14N and 28Si from 3 to 4 MeV

In this work commercially available self-supporting thin silicon-nitride films were applied to measure the differential cross sections for the reactions 28Si(p,p′γ)28Si (Eγ = 1779 keV) and 14N(p,p′γ)14N (Eγ = 2313 keV) in the proton energy range of 3–4 MeV. For an additional validation of the data, the cross section from the present work and from the literature were integrated and compared to experimental thick target yields. Gamma-rays were detected simultaneously with backscattered particles using a HPGe detector at 55° and an ion implanted Si detector at 135° with respect to the beam direction. As a by-product, differential gamma-ray and particle production cross sections were measured for the first time in the 29Si(p,p′γ)29Si (Eγ = 1273 keV) reaction at 55°, as well as in the natN(p,po)natN, natSi(p,po)natSi and 28Si(p,p1)28Si elastic and inelastic scatterings at 135° from 3 to 4 MeV proton energies.

Reduction of the Lorenz Number in Copper at Room Temperature due to Strong Inelastic Electron Scattering Brought about by High-Density Dislocations.

In this work, heat and charge transport were measured in a series of deformed bulk Cu samples where dislocation density was tuned but dislocation character generally remained unchanged. We observed a notable violation of the Wiedemann-Franz law at room temperature for such a conventional metal. We show that high-density dislocations introduce strong inelastic electron scattering, which relax heat and charge currents to different extents. A reduction of Lorenz number by 15% was observed. We reveal that the contribution from elastic scattering to the incremental thermal resistivity scarcely varies with dislocation density, but the contribution due to inelastic scattering monotonically increases and becomes overwhelmingly dominant for dislocation density above 1.0 × 1015 m-2.

Fingerprint Oxygen Redox Reactions in Batteries through High-Efficiency Mapping of Resonant Inelastic X-ray Scattering

Realizing reversible reduction-oxidation (redox) reactions of lattice oxygen in batteries is a promising way to improve the energy and power density. However, conventional oxygen absorption spectroscopy fails to distinguish the critical oxygen chemistry in oxide-based battery electrodes. Therefore, high-efficiency full-range mapping of resonant inelastic X-ray scattering (mRIXS) has been developed as a reliable probe of oxygen redox reactions. Here, based on mRIXS results collected from a series of Li1.17Ni0.21Co0.08Mn0.54O2 electrodes at different electrochemical states and its comparison with peroxides, we provide a comprehensive analysis of five components observed in the mRIXS results. While all the five components evolve upon electrochemical cycling, only two of them correspond to the critical states associated with oxygen redox reactions. One is a specific feature at 531.0 eV excitation and 523.7 eV emission energy, the other is a low-energy loss feature. We show that both features evolve with electrochemical cycling of Li1.17Ni0.21Co0.08Mn0.54O2 electrodes, and could be used for characterizing oxidized oxygen states in the lattice of battery electrodes. This work provides an important benchmark for a complete assignment of all mRIXS features collected from battery materials, which sets a general foundation for future studies in characterization, analysis, and theoretical calculation for probing and understanding oxygen redox reactions.

Transport responses from rate of decay and scattering processes in the Nambu–Jona-Lasinio model

We have calculated quark and anti-quark relaxation time by considering different possible elastic and inelastic scatterings in the medium. Comparative role of these elastic and inelastic scatterings on different transport coefficients are explored. The quark-meson effective interaction Lagrangian density in the framework of Nambu--Jona-Lasinio model is used for calculating both type of scatterings. Owing to a kinetic threshold, inelastic scatterings can only exist beyond the Mott line in temperature and chemical potential plane, whereas elastic scatterings occur in the entire plane. Interestingly, the strength of inelastic scatterings near and above Mott line becomes so strong that medium behaves like a perfect fluid, in that all transport coefficients become very small.

Vibrational Dynamics of Ferroelectric K(Ta1-xNbx)O3 Studied by Inelastic Light Scattering

The Fano resonance of non-doped KTa1-xNbxO3 (x = 0.32) single crystals was investigated by the Raman spectroscopy. The intensity of central peak (CP) and parameters of the Fano resonance revealed a significant anomaly in the vicinity of the Curie temperature, TC = 259 K. The vibrational dynamics and the symmetry breaking in the cubic phase are discussed in the framework of weak random fields. It is concluded that the coupling between continuum states induced by polar nanoregions (PNRs) and a transverse optic (TO2) phonon at about 194 cm−1 is the origin of a Fano resonance in non-doped KTN crystals.

Covariance Matrices for Differential and Angle-Integrated Neutron-Induced Elastic and Inelastic Scattering Cross Sections of 56Fe

Correlations between neutron inelastic scatterings angular distributions are not included in the Joint Evaluated Fission and Fusion (JEFF) nuclear data library, while they are key quantities for uncertainty propagation of nuclear data. By reproducing the angle-integrated cross sections and uncertainties of JEFF-3.1.1, the present work obtains covariance matrix between high energy model parameters using the least square method implemented in the CONRAD code. With this matrix, it is possible to generate correlations between angle-integrated cross sections and angular distributions, which are usually presented by Legendre coefficients. As expected, strong correlations are found, for example, between the Legendre coefficients of elastic and first-level-inelastic scatterings and the angle-integrated total, elastic, total inelastic cross sections.

Toroidal Modes in Nuclei by Inelastic Electron Scattering

Electron scattering is a tool that can provide relatively clean view of the nuclear structure in both ground and excited states, as it depends on the well-known electromagnetic interaction. But since the common expressions for its cross section were derived with certain assumptions, in this paper we describe several nontrivial steps necessary for a proper theoretical calculation within the current density-functional framework, namely with Skyrme QRPA for axial nuclei, with aim to enable comparison of the theoretically predicted low-lying $1^-$ toroidal modes with future (e,e') experiments.

Observation of Spin-State Transition of LaCoO3 by Using High-Resolution Co 2p Resonant Inelastic X-ray Scattering

Observation of Spin-State Transition of LaCoO₃ by Using High-Resolution Co 2<i>p</i> Resonant Inelastic X-ray Scattering

Nano-Scale Atomic Structures Appeared in Liquids―Atomic Dynamics Studies by Inelastic X-ray Scattering

Nano-Scale Atomic Structures Appeared in Liquids―Atomic Dynamics Studies by Inelastic X-ray Scattering

Theoretical calculation and evaluation of n + 240,242,244Pu reactions

The nuclear data of $${\text{n}}\,+\,^{240,242,244}$$ Pu reactions for incident energy below 200 MeV are calculated and evaluated to meet the requirement in the design of an accelerator-driven subcritical system. The optical model is used to calculate the total, nonelastic, shape elastic cross sections, shape elastic scattering angular distributions, and transmission coefficients. The distorted-wave Born approximation is applied to calculate the direct inelastic scatterings to the discrete excited states. The nuclear reaction statistical models and fission theory are applied to describe neutron, proton, deuteron, triton, helium-3, alpha and $$\gamma$$ emissions, and fission consistently. The results thus obtained are compared with experimental data and the evaluated data obtained from ENDF/B-VII.1 and JENDL-4.0.

Elastic and Inelastic Scattering of $^{15}$N Ions by $^{12}$C at 81 MeV and the Effect of Transfer Channels

Elastic and Inelastic Scattering of $^{15}$N Ions by $^{12}$C at 81 MeV and the Effect of Transfer Channels

Application of special relativity in damage calculations

The Displacement per Atom (DPA) is one of the most important factors that influence the mechanical behaviors of materials during and after irradiation. However, the relativistic effect is not accounted for in typical calculations of DPA cross sections and Primary Knock-on Atom (PKA) spectra. The present work shows the computation of relativistic recoil energy. For incident energy lower than 20 MeV, the relativistic corrections are within 1% for neutron scattering reactions of 56Fe and nuclei with mass larger than 56Fe. The corresponding corrections on damage energy (equivalent to DPA with standard DPA metrics) is smaller than 0.5%. However, the relativistic effect is of importance for high incident energies, such as 200 MeV. For example, the relativistic recoil energy of continuum inelastic scattering is 10% higher than the classical one for all nuclei. The consideration of relativistic effect increases the recoil energy for the elastic scattering. Both positive and negative relativistic corrections are possible for both discrete and the inelastic scatterings. A consequent result is the broadening of PKA spectra.