Scattering Cross Section Research Articles

Systematic study of global optical model potentials in (d, p) transfer reactions* *Supported by the National Natural Science Foundation of China (12035011, 11975167, 11535004, 11947211, 11905103, 11761161001, 11375086, 11565010, 11881240623, 11961141003), the National Key R&D Program of China (2018YFA0404403, 2016YFE0129300), the Science and Technology Development Fund of Macau (008/2017/AFJ) and the Fundamental Research Funds for the Central Universities (22120200101)

In the T-matrix form of the transfer reaction, the optical model potentials (OMPs) are used to compute the scattering wave function and transition operator. For most cases, the elastic scattering cross sections, normally used to generate the OMPs, are not directly given in the same experiment. Then, the global OMPs, which fit the experimental data over a broad mass and energy range, are widely used in the theoretical calculations. Different sets of global OMPs with different parameter sets can reproduce the scattering cross section equally well within the uncertainty. Here, we apply different global OMPs to calculate the (differential) cross sections of transfer reactions on the target nuclei , , , and at different energies. The results demonstrate that the effects of deuteron and nucleon global OMPs on transfer (differential) cross sections vary with energy and target mass. Furthermore, the influences of the spin-orbit coupling term of deuteron and nucleon global OMPs on the transfer cross sections are not negligible.

Bounds on boosted dark matter from direct detection: The role of energy-dependent cross sections

The recoil threshold of Direct Detection experiments limits the mass range of Dark Matter (DM) particles that can be detected, with most DD experiments being blind to sub-MeV DM particles. However, these light DM particles can be boosted to very high energies via collisions with energetic Cosmic Ray electrons. This allows Dark Matter particles to induce detectable recoil in the target of Direct Detection experiments. We derive constraints on scattering cross section of DM and electron, using XENONnT and Super-Kamiokande data. Vector and scalar mediators are considered, in the heavy and light regimes. We discuss the importance of including energy dependent cross sections (due to specific Lorentz structure of the vertex) in our analysis, and show that the bounds can be significantly different than the results obtained assuming constant energy-independent cross-section, often assumed in the literature for simplicity. Our bounds are also compared with other astrophysical and cosmological constraints.

The CH-3Σ+ Anion: Inelastic Rate Coefficients from Collisions with He at Interstellar Conditions.

We present accurate ab initio calculations on several properties of a gas-phase system of interest in the interstellar medium (ISM), where the title molecular anion has been often surmised but not yet confirmed by observations. The CH-3Σ+ constitutes the smallest term in the series of longer anionic polyynes which have been observed in the ISM (e.g., C4H- and several others). Hence, its dynamical behavior in collision with He atoms, one of the most abundant atoms in that environment, can provide quantitative indicators on the changes which can occur in the rotational state population of the title anion when driven by this collision dynamics. We therefore report an accurate evaluation of the full potential energy surface (PES) which acts between the molecular anion in its ground vibrational state and the He atom. The relevant inelastic scattering cross sections and the corresponding inelastic rate coefficients are then computed within a quantum treatment of the collisions. We find that the fairly small values of the final inelastic rate coefficients indicate state-changing processes by collisions to be inefficient paths for modifying the rotational state populations of this anion and therefore to aid its possible observation from direct radiative emission in the microwave region.

Excitation and fragmentation of the dielectric gas C4F7N: Electrons vs photons.

C4F7N is a promising candidate for the replacement of sulfur hexafluoride as an insulating medium, and it is important to understand the chemical changes initiated in the molecule by collision with free electrons, specifically the formation of neutral fragments. The first step of neutral fragmentation is electronic excitation, yet neither the absorption spectrum in the vacuum ultraviolet (VUV) region nor the electron energy loss spectrum have previously been reported. Here, we experimentally probed the excited states by VUV photoabsorption spectroscopy and electron energy loss spectroscopy (EELS). We found that the distribution of states populated upon electron impact with low-energy electrons is significantly different from that following photoabsorption. This difference was confirmed and interpreted with ab initio modeling of both VUV and EELS spectra. We propose here a new computational protocol for the simulation of EELS spectra combining the Born approximation with approximate forms of correlated wave functions, which allows us to calculate the (usually very expensive) scattering cross sections at a cost similar to the calculation of oscillator strengths. Finally, we perform semi-classical non-adiabatic dynamics simulations to investigate the possible neutral fragments of the molecule formed through electron-induced neutral dissociation. We show that the product distribution is highly non-statistical.

Excitations of H2 by positron impact

In this paper, we present a theoretical study of scattering cross sections for positron impact of electronic states of hydrogen molecule (H2) using the scaling Born positron (SBP) approach. Cross sections to low-lying electronic states, B1∑+u, C1Пu, B´1 ∑+u, and D1Пu are investigated. In an earlier theoretical effort [J.L.S.Lino, Rev. Mex. Fisica 62 (2016) 596], an application of the SBP approach for the X1∑+g - > B1∑+u electronic excitation of the H2 molecule, gave cross sections with reasonable qualitative agreement with experimental data [J.P.Sullivan et. al., Phys.Rev.Lett.87,073201 (2001)]. However, recent studies for the excitation of the B1∑+u state by positron impact showed that this electronic state still demand of a refined degree of description of the quality of the cross sections (Weiss et. al., Eur. Phys. J. D (2018) 72). The purpose of this work was to reexamine the B1∑+u state and verify the quality of the numerical convergence of SBP method and extend the investigation to other states. The possibility to estimate a indirect contribution of multichannel effects ( three states considering the ground X1, B1∑+u and E,F1∑+u state) are introduced within the SBP context. For the first time, integral cross sections to these new states using the SBP approach are reported. In the absence of the experimental data and theoretical developments, comparisons are made with analogous electron scattering.

Size quantification of non-spherical bubbles by ultrasound

Ultrasonic detection is an effective method to quantify bubbles in opaque liquid, and acoustic scattering model is the key in ultrasonic inversion technique. Classical scattering models are usually based on the spherical assumption, and <i>ka</i> is much less than 1. However, these conditions are not always satisfied in practical applications. In this study, a quantitative strategy of ultrasonic inversion is proposed for non-spherical bubbles and <i>ka</i> deviation assumption. A series of solution models for a spherical gas bubble is established without considering the <i>ka</i> constraint, and it is compared with the classical Medwin (<inline-formula><tex-math id="Z-20230117094142">\begin{document}$ka\ll1 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20222074_Z-20230117094142.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20222074_Z-20230117094142.png"/></alternatives></inline-formula>) and Anderson (<i>ka </i>≈ 1) models. The difference in scattering cross section <i>σ</i><sub>bs</sub> betweem them is only at the higher order formants of scattering, so the fitted line can be used to solve the multi-valued problem between <i>σ</i><sub>bs</sub> and <i>ka</i>. For a non-spherical bubble, <i>σ</i><sub>bs</sub> is determined by the frequency domain backscattering signal, the size is characterized by the equivalent radius<i> a</i><sup>*</sup>, and the inversion is performed by fitted curve from series solution model. Ultrasonic quantitative results are examined by high-speed photography. Results show that during the bubbles rising along a zigzag path, they develop non-spherical bubbles, their scattering cross sections are measured by the frequency domain scattering signal obtained at a position of ultrasonic measurement, and the equivalent radius is inverted by the series solution fitting curve. The deviation of the result from the actual result <i>r</i><sub>0</sub> is about 1mm (relative error less than 45%) when 9≤<i>kr</i><sub>0</sub>≤35. This method can be used for implementing the acoustic inversion of non-spherical bubbles in a certain range of measurement accuracy.

A benchmark study of large-angle neutron scattering cross section of tungsten using two shadow bars technique at 14 MeV

In fusion reactor design, neutron leaks intensively from blanket material through a gap. In this streaming phenomenon, backscattering cross section is known to be very crucial. In the present study, the author's team carried out a new experiment for benchmarking the large angle scattering cross section of tungsten using a DT neutron source of OKTAVIAN facility, Osaka University, Japan. Tungsten-containing material is under consideration as the radiation shield in a fusion reactor. The experimental geometry consists of a DT neutron source, two shadow bars, niobium foil, and a tungsten target. Four irradiations were performed at a neutron energy of 14 MeV using DT neutrons to extract only the contribution of large angle scattering cross section. By using two shadow bars, room return contribution was effectively suppressed. Consequently, only backscattering neutrons were measured by using a niobium foil. In the present benchmark study, obtained experimental data were compared with numerical calculations by MCNP6 using various nuclear data libraries, including JENDL-4.0, JENDL-5, JEFF-3.3, and ENDF/B-VIII.

Effects of Hydrogen Bonding on Nuclear Data Development of Liquid Anhydrous HF

Anhydrous Hydrogen Fluoride (HF) at high temperatures and pressures is used to process and manufacture nuclear fuel. As HF is often used directly with uranium, correct neutron thermal scattering cross sections are crucial to criticality safety applications. Classical molecular dynamics (CMD) simulation of the flexible HF system was used to create the thermal scattering law (TSL) and cross sections. The initial 2-site model is used in LAMMPS, and it can not capture the H-bond. To correctly represent the H-bond effects, a second, 3-site model was constructed in GROMACS. The 3-site model handled H-bonds by connecting a massless charge to the molecule. Key model parameters were compared to experimental data to verify the approach and models. To get the normalized VACF, the model was compared using hydrogen and fluorine bond length, density, potential energy, and diffusion coefficient. The phonon DOSs for both models were derived from the normalized VACF. DOSs were used to estimate the TSL (S(α,β)) and neutron thermal scattering cross sections for hydrogen in HF. The TSLs were evaluated using the FLASSH code with the Schofield diffusion model. It was observed that the representation of the hydrogen bonding changes the TSL's diffusional contributions. This is represented in the low energy scattering cross section, where intermolecular binding effects shift the cross section.

Theoretical calculations of neutron scattering cross sections for tetrahydrofuran-containing clathrate hydrates at low temperature

Tetrahydrofuran-containing clathrate hydrate is considered as a potential cold and very cold neutron moderator material. The fully deuterated form is more promising because of the lower neutron absorption cross section of deuterium. In this work we present theoretical calculations of neutron scattering cross sections for hydrogenated and deuterated clathrates at low temperature. The scattering cross sections are generated by using the crystalline structure and phonon density of states obtained from density functional theory calculations. The theoretical neutron scattering cross sections serve to compare against existing or future experimental data.

О применимости универсальной функции Линдхарда для описания сечений рассеяния атомных частиц

It is shown that the application of the universal Lindhard function for calculating the scattering cross section of atomic particles is, as a rule, limited to the region of scattering angles less than 20. The results obtained for various popular interaction potentials are compared with the available experimental data. It is shown that the presence of inelastic channels in scattering leads to the appearance of additional maxima in the scattering cross section. Recommendations are given on the use of the universal Lindhard function to describe quasi-elastic scattering in the region =·sin(/2)>0.01,  is the reduced impact energy,  is the scattering angle. At high energies, the scattering is well described by screened Coulomb potentials, and the application of the Lindhard function provides an accuracy of 10% for calculating the scattering cross sections.

Evaluation of Thermal Neutron Scattering Law and Cross Sections for Calcium Hydride

Presented here are the calculated thermal scattering law (TSL) and thermal neutron scattering cross sections for Calcium Hydride, hereafter referred to by its chemical symbol CaH2. The only other such data prior to this evaluation are thermal neutron scattering libraries in the JEFF database, which do not fully capture the scattering physics of the CaH2 system. The data in this evaluation are calculated from first principles; Density Functional Theory (DFT) is used to calculate the phonon density of states (DOS), which is the primary input required to derive the TSL. The TSL and cross sections have been evaluated for the three non-equivalent atom cites in the CaH2: Ca, H1, and H2. Each evaluation has been submitted to the NNDC for consideration in the next ENDF/B database release.

A Study on Electromagnetic Scattering Characteristics of 4-D Antenna Arrays

A theoretical study on electromagnetic scattering mechanism of 4-D antenna arrays is performed for the first time. First, the scattering fields of one antenna element within an infinite 4-D array are derived under periodic boundary conditions. In order to estimate the scattering performances of 4-D antenna arrays, numerical models of the scattering fields are then established based on the traditional scattering pattern multiplication theory. Moreover, an effective time-domain full-wave approach is proposed for the scattering cross section (SCS) simulation of 4-D arrays. Finally, to verify the feasibility for SCS reduction through 4-D arrays, the differential evolution (DE) algorithm is adopted to synthesize a 14-element microstrip patch antenna array for the optimization of radiation and scattering performances. Numerical results show that 4-D arrays are capable of scattering the incident waves in both space domain and frequency domain simultaneously, thus accomplishing remarkable in-band SCS reduction.

From 232Th(n, n’γ) cross sections to level production and total neutron inelastic scattering cross sections

To probe the neutron inelastic scattering off 232Th, an experiment took place at the EC-JRC Geel conducted with the experimental setup GRAPhEME to detect emitted γ-rays. The prompt γ-ray spectroscopy method was used and 70 experimental 232Th(n, n’γ) cross sections were obtained from the experimental data. Combining these cross sections, nuclear-structure data available in databases and hypotheses to complete the latter, neutron inelastic level production cross sections in 232Th and the total inelastic cross section were calculated. For the first time, the total inelastic cross section of an actinide nucleus was derived on the total neutron energy range from experimental data only. Comparisons of (n, n’) cross section data with evaluated data reveal a good agreement between them all above 300 keV of neutron energy. TALYS calculations are compatible but lower than the evaluated data.

Chemical conjugation to differentiate monosaccharides by Raman and surface enhanced Raman spectroscopy.

Sugars play important roles in numerous biological processes, from providing energy to modifying proteins to alter their function. Glycosylation, the attachment of a sugar residue to a protein, is the most common post translational modification. Identifying the glycans on a protein is a useful tool both for pharmaceutical development as well as probing the proteome and glycome further. Sugars, however, are difficult analytes to probe due to their isomeric nature. In this work, Raman spectroscopy and surface enhanced Raman spectroscopy (SERS) are used to identify different monosaccharide species based on the vibrational modes of these isomeric analytes. The weak scattering of the sugars was overcome through conjugation with phenylboronic acid to provide a larger Raman scattering cross section and induce slight changes in the observed spectra associated with the structure of the monosaccharides. Spontaneous Raman, SERS in flow, and static SERS detection were performed in order to discriminate between arabinose, fructose, galactose, glucose, mannose, and ribose, as well as provide a method for identification and quantification for these sugar conjugates.

FLASSH 1.0: Thermal Scattering Law Evaluation and Cross Section Generation

The Full Law Analysis Scattering System Hub (FLASSH) is an advanced code which evaluates the thermal scattering law (i.e. TSL, S(α,β)) for thermal scattering cross sections and resonance Doppler broadening. The ability to accurately capture these two key cross section features is dependent on accurate, high fidelity TSL evaluations. FLASSH 1.0 provides advanced physics capabilities resulting in an improved, generalized TSL to most accurately represent the lattice dynamics within any material. This improved TSL will allow for consistent analysis in both the thermal and epithermal energy ranges. The features for TSL analysis are packaged within the FLASSH GUI for easy user interface along with data output in many file formats including ENDF File 7 and ACE files.

Упругое рассеяние атома рутения на атомах Si и O в диапазоне относительных кинетических энергий 2-200 eV

Interconnector technologies of a new generation involve use of ruthenium. The high cost of experimental study of sputtering and etching of trenches in Ru leads to the need to optimize it by modeling, requiring knowledge of the cross sections of elementary processes of interaction of plasma particles with Ru. In this work, the binary interatomic potentials of Ru-Ru and Ru-Si pairs, tested by molecular dynamics method, and the Ru-O one calculated using the multi reference configurational interaction MRCI/AV5Z were used to calculate the elastic scattering cross sections of the atomic pairs in the energy range typical for plasma etching chambers.

Design study of benchmark experiment for large-angle scattering cross section for non-solid target with 14 MeV neutron

Accuracy of large-angle scattering cross section in nuclear data has a large contribution on precision of neutron transport calculation in fusion reactor design. In the previous research, benchmark experiments for a solid target were carried out, however, non-solid targets, which are enclosed in a container, could not be dealt with. This is because we were not able to remove the effect due to existence of the container in the previous method. In this study, we performed design study of advanced benchmark experiment for large-angle scattering cross section especially for a non-solid target in a container. In addition, we also carried out benchmark experiments for silicon, which is important for the fusion reactor, however, is one of the elements that are difficult to obtain a solid target. In conclusion, we successfully developed an advanced benchmark experimental method for non-solid targets and verified it numerically by Monte Carlo calculation. In addition, we also found experimentally that large-angle scattering cross section of silicon is underestimated in JENDL-4, ENDF-B/VIII and JEFF-3.3.

Description of quantum interference using mixed quantum/classical theory of inelastic scattering.

Manifestation of the quantum interference effect in the oscillation of scattering cross section is explored using the N2 + O system as a case study. Calculations are carried out for two electronic PESs of the system, for various initial rotational states of N2, in a broad range of N2 + O collision energies and using three theoretical methods: two versions of the approximate mixed quantum/classical theory (MQCT and AT-MQCT) and the accurate full-quantum coupled-channel method (implemented in MOLSCAT). A good agreement between different methods is observed, especially at high energies. Elastic scattering cross-sections oscillate as a function of collision energy, which is the result of quantum interference. The effects of initial rotational excitation and of the PES properties are studied in detail. For the final (thermally averaged) cross sections, both MOLSCAT and MQCT calculations predict a rather regular pattern of quantum oscillations that persist through a broad range of collision energies and expand into the low-energy regime where quantum scattering resonances are common. The difference between cross sections predicted by MQCT and MOLSCAT decreases from ∼8% at low energies to ∼2% at high energies. Experimental data available at high collision energies are well reproduced.

Enhanced microwave absorption performance of large-sized monolayer two-dimensional Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> based on loaded Fe<sub>3</sub>O<sub>4</sub> nanoparticles

With the rapid development of electronic equipment, electromagnetic interference and electromagnetic radiation pollution have become serious problems, because excessive electromagnetic interference will not only affect normal operation of electronic equipment but also do great harm to human health. In general, an ideal material for microwave absorption with the characteristics of high reflection loss (RL) intensity, wide effective absorption band (EAB), thin thickness, and lightweight could effectively consume electromagnetic wave (EMW) energy. Therefore, it is crucial to search for such an ideal microwave absorption material to deal with the electromagnetic radiation pollution. Two-dimensional (2D) carbon/nitride MXene has received more and more attention in recent years, because excellent electrical conductivity and rich surface-functional groups in MXene show positive effects on electromagnetic wave absorption. However, as a non-magnetic material with only dielectric loss, MXene exhibits obvious impedance mismatch, which greatly limits its practical applications. Combining MXene with magnetic materials becomes a hotspot for the exploration of ideal microwave absorption materials. As a typical ferrite, Fe<sub>3</sub>O<sub>4</sub> shows excellent soft magnetic properties such as high saturation magnetization, high chemical stability, and simple preparation. In this paper, the 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite is successfully prepared by hydrothermal method and simple electrostatic adsorption process. The Fe<sub>3</sub>O<sub>4</sub> nanoparticles are uniformly anchored on the surface of large-sized monolayer Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>, which effectively reduces the stacking of MXene. By regulating the proportion of magnetic materials, the microwave absorption performance of 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite is investigated. With the content of Fe<sub>3</sub>O<sub>4</sub> nanoparticles in the 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite increasing from 4 mg to 8 mg, the microwave absorption performance is enhanced obviously. This is caused by the abundant Fe<sub>3</sub>O<sub>4</sub>/Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> interface, scattering channels, point defect, charge density difference in 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite, and the optimized impedance matching. The minimum reflection loss (RL<sub>min</sub>) of 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite reaches –69.31 dB at a frequency of 16.19 GHz, and the effective absorption band (EAB) achieves 3.39 GHz. With the content of Fe<sub>3</sub>O<sub>4</sub> nanoparticles further increasing to 10 mg, the microwave absorption performance shows a decreasing trend. Excessive Fe<sub>3</sub>O<sub>4</sub> nanoparticles in the 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite lead to the decrease of electrical conductivity and thus the impedance dis-matching and dielectric loss decreasing, which leads the microwave absorption performance to decrease. Radar scattering cross section (RCS) is a physical quantity that evaluates the intensity of the scattered echo energy in the intercepted electromagnetic wave energy. The results of the RCS simulation can be applied to real objects which have been widely utilized in radar wave stealth. Its multi-angle simulation results can be used as an important basis for evaluating the stealth capability of microwave-absorbing material. The RCS simulations show that the average RCS value of 2D Fe<sub>3</sub>O<sub>4</sub>@Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> composite is over –47.92 dBm<sup>2</sup> at an incidence angle of 25°, demonstrating its excellent radar wave absorption performance. This study provides new ideas for improving and practically using two-dimensional and magnetic materials in the microwave absorption field and gives a new path to the subsequent development of microwave-absorbing composites.

Neutron thermal cross sections of 3D-printing organic polymers using the Average Functional Group Approximation

We provide a worked example on how to obtain the total neutron scattering cross section of organic polymers at thermal neutron energies by means of the Average Functional Group Approximation. Within this framework, a polymer is rationalised as composed of hydrogen atoms belonging to specific functional groups,therefore taking into account the material-specific incoherent inelastic scattering contributions to the thermal cross section. Such simplified model allows the calculation of thermal neutron cross sections for a broad variety of materials of interest in neutron applications, e.g., sample containers and shielding components. We discuss in detail the case of ABS, often available as a 3D-printing material, whereby three polymers (acrylonitrile, butadiene, and styrene) can be combined in several mass percentages depending on the final application. Results are obtained using the NCrystal module already featuring the Average Functional Group Approximation.