Scattering Spectra Research Articles

Design, Preparation and Surface-enhanced Raman Scattering(SERS) Spectrum of Single Ag Nanodot†

Design, Preparation and Surface-enhanced Raman Scattering(SERS) Spectrum of Single Ag Nanodot†

Vibrational dynamics of 4-fluorobenzaldehyde from periodic DFT calculations

A thorough vibrational portrait of 4-fluorobenzaldehyde is presented, covering Infrared (Mid- and Far-), Raman and Inelastic Neutron Scattering (INS) spectra. Periodic DFT calculations (CASTEP) of a model 4FB crystal proved useful for vibrational assignment, yielding estimates of experimental spectra with near one-to-one correspondence – including the correct estimation of overtone and combination modes. A striking similarity among the Far-IR spectrum of liquid 4FB and that estimated based on a periodic structure indicates that the solid-liquid transition induces soft structural changes which leave most vibrational modes unaffected – except for those directly involved in CH…O bonding, where crystal field splitting is observed.

Resonant Inelastic X-ray Scattering and Nonesonant X-ray Emission Spectra from Coupled-Cluster (Damped) Response Theory

A coupled cluster protocol rooted in damped response theory is presented for computing Resonant Inelastic X-ray Scattering spectra of molecules in gas-phase. Working equations are reported for both linear (i.e., equation-of-motion) and nonlinear parametrizations of the coupled-cluster wave function response. A simple scheme to compute nonresonant X-ray Emission Spectra is also proposed. Illustrative results are presented for water.

Fast analysis of collective Thomson scattering spectra on Wendelstein 7-X.

Two methods for fast analysis of Collective Thomson Scattering (CTS) spectra are presented: Function Parametrization (FP) and feedforward Artificial Neural Networks (ANNs). At this time, a CTS diagnostic is being commissioned at the Wendelstein 7-X (W7-X) stellarator, with ion temperature measurements in the plasma core as its primary goal. A mapping was made from a database of simulated CTS spectra to the corresponding ion and electron temperatures (Ti and Te ). The mean absolute mapping errors are 4.2% and 9.9% relative to the corresponding Ti , for the ANN and FP, respectively, for spectra with Gaussian noise equivalent to 10% of the average of the spectral maxima in the database at 650 sampling points per GHz and within a limited parameter space. Although FP provides some insight into the information contents of the CTS spectra, ANNs provide a higher accuracy and noise robustness, are easier to implement, and are more adaptable to a larger parameter space. These properties make ANN mappings a promising all-round method for fast CTS data analysis. Addition of impurity concentrations to the current parameter space will enable fast bulk ion temperature measurements in the plasma core region of W7-X.

Optical nonlinearity and charge transfer analysis of 4-[(E)-2-(2,4,6-Trinitrophenyl) ethylidene] benzonitrile adsorbed on silver nanoparticles: Computational and experimental investigations

The search for a potential nonlinear optical (NLO) material has led to the investigation of an organic compound 4-[(E)-2-(2,4,6-Trinitrophenyl)ethylidene]benzonitrile (TEB), which has a possibility of enhancing the NLO properties by the charge transfer mechanism if metal atoms are adsorbed on it. The experimental characterization of TEB is done using Fourier Transform Infrared (FT-IR), FT-Raman, Ultraviolet–visible (UV–Visible), Photoluminescence (PL), Thermogravimetric/Differential Thermal Analysis (TG/DTA) and Z-scan techniques. The third order NLO properties evaluated using Z-scan technique proves that the material can be used as a good optical limiter. TEB is attached with silver atoms and the theoretical studies including geometry optimization, NBO analysis and hyperpolarizability calculations are carried out. The TEB molecule with silver atoms adsorbed is found to have increased hyperpolarizability values. The charge transfer from the metal atom to the nitrile group of the molecule is evident from the Surface Enhanced Raman Scattering (SERS) spectra using the silver nanoparticles.

Interactions of high-order Bessel vortex beam with a multilayered chiral sphere: Scattering and orbital angular momentum spectrum analysis

Analytical solution to the scattered field and near-surface field of a multilayered chiral sphere illuminated by a high-order Bessel vortex beam (HOBVB) are investigated. Using the vector wave theory, the expansion coefficients of a HOBVB in terms of spherical vector wave functions (SVWFs) are derived. Based on the fields expansion in each region and continuous boundary condition at each interface, the expansion coefficients of the sphere are solved by constructing the iterative form of the coefficients equations. Influences of the topological charge, half-cone angle and chirality on the scattering pattern of far region and near-surface field are analyzed in detail. In addition, the intensity and phase distributions at the transverse plane after interaction are presented for on- and off-axis incidences. Comparisons of orbital angular momentum (OAM) spectrum indicate that off-axis incidence results in topological charge shift from the incident case, and the farther from the axis and the more complex the particles, the more serious the phase distortion. The results provide insights into the scattering and light-matter interactions and may find important applications in optical propagation and multicasting optical communication.

First-Principles Estimation of Electronic Temperature from X-Ray Thomson Scattering Spectrum of Isochorically Heated Warm Dense Matter

Through the perturbation formula of time-dependent density functional theory broadly employed in the calculation of solids, we provide a first-principles calculation of x-ray Thomson scattering spectrum of isochorically heated aluminum foil, as considered in the experiments of Sperling etal. [Phys. Rev. Lett. 115, 115001 (2015)PRLTAO0031-900710.1103/PhysRevLett.115.115001], where ions were constrained near their lattice positions. From the calculated spectra, we find that the electronic temperature cannot exceed 2eV, much smaller than the previous estimation of 6eV via the detailed balance relation. Our results may well be an indication of unique electronic properties of warm dense matter, which can be further illustrated by future experiments. The lower electronic temperature predicted partially relieves the concern on the heating of x-ray free electron laser to the sample when used in structure measurement.

Effect of different microwave power applied during microwave assisted radiant heating on the structure, dielectric and electrical properties of Ba0.8 Ca0.2 TiO3 ceramics

Microwave assisted radiant heating (MARH) is hybrid sintering technique, where conventional radiant heating is accompanied by precisely controlled different microwave power (Mw) percentages. Lead-free polycrystalline samples of (Ba, Ca) TiO3 BCT ceramics derived from hydrothermal process were synthesized by MARH technique. A systematic study has been carried out to examine the effect of different microwave power (Mw) percentages applied during MARH on the structure, dielectric and electrical properties of BCT samples. Room temperature X-ray diffraction pattern and Raman Scattering spectra revealed formation of single phase tetragonal structure for all the samples and tetragonality increases with increasing Mw power percentages. However, the dielectric permittivity shows maximum increment (e′ ~ 16,000) for the samples sintered with 30 Mw power percentage. Impedance spectroscopic analysis suggested negative temperature coefficient of resistance (NTCR) behavior with non-Debye type dielectric relaxation. Electrical resistivity also increases with increasing Mw power percentages for all the samples. Samples sintered with 30 Mw power percentage exhibited enhanced dielectric and electrical properties.

Biocompatible Au@Carbynoid/Pluronic-F127 nanocomposites synthesized by pulsed laser ablation assisted CO2 recycling

Ligand-free carbynoid-encapsulated gold nanocomposites (Au@Carbynoid NCs) with blue-shifted localized surface plasmon resonance (LSPR) have been synthesized by CO2 recycling induced by pulsed laser ablation (PLA) of a solid gold target in aqueous solution with NaOH at pH 7.0. High Resolution Transmission Electron Microscopy (HRTEM) images at not destructive acceleration voltage of 80 kV revealed carbynoid nanocrystals around the gold core, associated to the intense bond length alternation (BLA) Raman mode of the carbon atomic wires (CAWs), centered at 2124 cm−1, observed in the Surface Enhanced Raman Scattering (SERS) spectra. It was verified that interlinking process with sp to sp2 conversion of the CAWs is induced both by high acceleration voltage in HRTEM and high irradiance of the excitation beam used in SERS measurements. Post synthesis mixing of Pluronic-F127 copolymer with pre-synthesized Au@Carbynoid NCs allows the formation of a fully biocompatible colloidal solution of Au@Carbynoid/Copolymer NCs. SERS investigation highlights that the Raman band of the BLA mode can be used as efficient Raman tag to monitor the functionalization of the NCs with the copolymer. The biocompatibility of the NCs was demonstrated performing a study of cytotoxicity using human skin fibroblasts. As proof of principle, it was demonstrated that the photodynamic activity of the bifunctional Au@Carbynoid/PF127 NCs in the presence of chlorin e6 (Ce6) drug can be enhanced inducing the aggregation state of the colloidal suspension. The stability of the colloidal dispersions of Au@Carbynoid NCs functionalized with Pluronic-F127 is verified after centrifugation in PBS (0.15 mol L−1 NaCl) solutions, confirming the possibility to use the green carbynoid based NCs as drug-carrier in biological applications.

Towards a Surface Enhanced Raman Scattering (SERS) spectra database for synthetic organic colourants in cultural heritage. The effect of using different metal substrates on the spectra

Two different silver colloids were synthetized using the reducing agents sodium citrate (Lee-Meisel method) and hydrochloric hydroxylamine (Leopold-Lendl method). The properties of these colloids were evaluated by investigating a selection of 25 synthetic organic dyes and pigments that belong to different chemical classes and whose Raman spectra are usually poor or are overwhelmed by fluorescence. The observed changes in the SERS spectra acquired using both colloids were evaluated and interpreted by taking into account that enhancement of the Raman signal is influenced by the localised plasmon resonance on the silver nanoparticles as well as by the chemical affinity and molecule orientation on the metal substrate. The morphology and plasmon resonance of the single nanoparticles were characterised by means of UV–Vis absorption spectroscopy. The results revealed significant differences in terms of stability and reproducibility. Furthermore, the sensitivity of the colloids and the reproducibility of the different measurements were evaluated in terms of the Raman shift and signal intensity. SERS spectra of triarylcarbonium (BV 14, BG 1, AB 110, AB 83, PB 1, PG 1) and xanthene colourants without halogen substituents (BV 10, PV 1, BR 1, PR81) as well as the nitro dye AY 24 were very reproducible with both colloids; however, others, such as brominated xanthene dyes (AR 87, AR 91), thioindigo pigments (PR 88, PR 181) and anthraquinone colourants, may present different spectral features depending on the colloid used, which should be taken into account when interpreting unknown spectra. The hydroxylamine-reduced colloid, besides being a reproducible and easy-to-produce SERS substrate, gave satisfactory spectra with all the SERS-active dyes and pigments that were examined. Based on the results, we assume that the hydroxylamine-reduced substrate is the best choice for acquiring spectra for a future SERS database for cultural heritage (CH) applications.

A Facet-Based Simulation of the Multipath Effect on the EM Scattering and Doppler Spectrum of a Low-Flying Target at Maritime Scene

A hybrid facet-based electromagnetic scheme is developed in this letter to investigate the multipath effect on the electromagnetic scattering and the Doppler spectrum of a low-flying target at maritime scene. In the scheme, the target and sea surface are both facetized. The facet-based small slope approximation method is developed to calculate the scattering upon the sea facet, which involves the composite scattering mechanisms upon both the long wave and short wave structures. The geometrical optics and physical optics method are combined with the fast ray-tracing technique in consideration of the multipath scattering. The equivalent edge current method is used to consider the scattering from the edged structures on the target. The tapered wave is used in the calculation process to eliminate the nonphysical edge diffractions. Numerical simulations present the multipath effect on the radar scattering characteristics of a low flying missile-like target above the sea surface. The Doppler spectra of the multipath scattering from the target flying at the time-evolving maritime scene are eventually simulated. The multipath effect is also investigated in the Doppler domain.

基于受激布里渊散射及紫外-可见吸收光谱的橄榄油等级鉴别与分析

基于受激布里渊散射及紫外-可见吸收光谱的橄榄油等级鉴别与分析

基于SFLA-LSSVM算法的多峰Brillouin散射谱的特征提取

基于SFLA-LSSVM算法的多峰Brillouin散射谱的特征提取

镉(Ⅱ)的共振散射光谱研究及应用

镉(Ⅱ)的共振散射光谱研究及应用

基于径向基函数神经网络直接提取布里渊散射谱温度的方法

基于径向基函数神经网络直接提取布里渊散射谱温度的方法

Manifestation of a strong quadrupole interaction and peculiarities in the SERS and SEHRS spectra of 4,4'-bipyridine

The paper analyzes Surface Enhanced Raman Scattering (SERS) and Surface Enhanced Hyper Raman Scattering (SEHRS) spectra of 4,4'-bypiridine molecule for two possible geometries, which are described by D2 and D2h symmetry groups. It is pointed out on appearance of sufficiently strong lines, caused by vibrations with the unit irreducible representation for both possible configurations. Appearance of these lines in the SEHRS spectrum points out the existence of a strong quadrupole light-molecule interaction. In addition one observes the lines, caused by vibrations both with the unit irreducible representations A or Ag and the irreducible representation B1 or B1u. The last ones describe transformational properties of the dz component of the dipole moment, which is perpendicular to the surface. This property of the spectrum is caused by peculiarity of the geometry of the molecule, which consists of two benzene rings, which are weakly connected with each other. The linear combinations of the vibrations of the rings create two nearly degenerated symmetric and anti symmetrical states, which cannot be identified in the experimental spectra. The result is in a full agreement with the dipole-quadrupole theory of SERS and SEHRS.

Core-hole Effect on Partial Electronic Density of State and O K-edge x-ray Raman Scattering Spectra of High-Pressure SiO2 Phases

Core-hole Effect on Partial Electronic Density of State and O K-edge x-ray Raman Scattering Spectra of High-Pressure SiO2 Phases

Детектирование спектров комбинационного рассеяния света высокого спектрального разрешения в коротких олигонуклеотидах: сравнение со спектрами полноразмерных ДНК

Детектирование спектров комбинационного рассеяния света высокого спектрального разрешения в коротких олигонуклеотидах: сравнение со спектрами полноразмерных ДНК

Deposition of diamond-like carbon thin films by the high power impulse magnetron sputtering method

The goal of the conducted experiments was to evaluate if the increased density of the plasma in High Power Impulse Magnetron Sputtering (HiPIMS) argon discharge would give the possibility of obtaining diamond-like films with high sp3 fraction content at room temperature. The magnetron cathode was driven by the self-designed supply. It consisted of high voltage supply, tank capacitors and a set of switches. The tank capacitors and the inductances of connecting wires formed an LC resonant circuit. As a result, each sputtering pulse (duration of 20μs, peak current of 1500–2200A) was followed by the inverse pulse (duration of 25μs, peak current of 400–700A), both having a sinusoidal shape. The repetition time was 3s. The silicon substrates were placed 8cm above the target surface. The sputtering processes of 99.99% pure graphite target were conducted in argon atmosphere at a pressure of 6–8×10−3hPa. The carbon films obtained after 400 deposition pulses had a thickness of 35nm. The surface RMS roughness, measured using an optical profiler, was about 2nm. The refractive index was estimated by means of ellipsometric studies to be 2.45 and 2.3 at 400 and 800nm, respectively. The sp3 hybridization fraction content of about 70–80% was calculated based on the analysis of Raman Scattering spectra.

Plasmon resonances in a silver elliptical cylinder surrounded by a confocal elliptical glass shell

Plasmon resonances occurring in a 2D problem of diffraction of a plane wave by a silver cylinder enclosed in a glass shell are studied under the assumption that the media interfaces are shaped as confocal ellipses. Scattering and absorption spectra in the optical range are calculated using strict numerical techniques. The obtained analytical expressions allow resonance parameters of the structure to be obtained in the quasi-static approximation.