Raman Spectrum and Thermal Stability of a Newly Developed TeO_2-BaO-BaF_2-La_2O_3-LaF_3 Glass

In this work, a new TeO2-BaO-BaF2-La2O3-LaF3 oxyfluorotellurite glass system is investigated. Differential thermal analysis (DTA) and structural analysis by Raman scattering spectra are reported on the glasses. The DTA results indicated that an increase of fluoride content in the glasses decreases the glass transition temperature (Tg) and increases the crystallization onset temperature (Tx). As a result the 70TeO2·20BaF2·10LaF3 glass showed a large Hruby's parameter, possessing excellent thermal stability. Changes in glass network structure with fluoride content are discussed based on the Raman scattering spectra of glasses. The glass network structures in the 70TeO2·4(20-x)BaO·xBaF2·(10-y)La2O3·yaF3 glasses are basically composed of both Te(O, F)4 and Te(O, F)3 units, but the Te(O, F)4/Te(O, F)3 ratio in the glass becomes higher with increasing fluoride content. This may be considered one of the reasons why the 70TeO2·20BaF2·10LaF3 glass exhibits excellent thermal stability.

Studies on Lattice Vibrational Modes of Na_5Eu(WO_4)_4 Single Crystal by Raman Spectrum

Raman and infrared spectra of host luminescent crystal Na_5Eu(WO_4)_4 in several different geometric con- figurations have been investigated.The symmetrical species of lattice vibrational modes of the crystal have been analysed by means of the site group analysis method of group theory.The experimental vibrational modes have been assigned to A_g,B_g,E_g,A_u and E_u of crystal factor group C_(4h).Because the energies of stretching vibrational modes of(WO_4)^(2-)ion groups are very high(in the range of 755～940 cm^(-1)),multiphonon nonradiative transitions of ~5D_2→~5D_1 and ~5D_1→~5D_0 in Eu^(3+)will occur.So it causes Eu^(3+)ions in Na_5Eu(WO_4)_4 to emit ~5D_0→~5F_j(j=1,2,3,4)emissions mainly at room temperature and the emission light of Na_5Eu( WO_4)_4 has high red colour purity.

Raman spectrum study of δ-doped GaAs/AlAs multiple-quantum wells

Three samples of GaAs/A1As multiple-quantum wells with different quantum well widths and tS-doped with Be ac- ceptors at the well center were grown on （100） GaAs substrates by molecular beam epitaxy. Polarized Raman spectra were recorded on the three samples at temperatures in a range of 4-50 K in a backscattering configuration. The two branches of coupled modes due to the interaction of the hole intersubband transitions and the quantum-well longitudinal optical （LO） phonon were observed clearly. The evaluation formalism of the Green function was employed and each lineshape of the Raman spectrum of the coupled modes was simulated. The dependence of the peak position of Raman shifts of the two coupled modes as well as the quantum-well LO phonon on the quantum-well size and measured temperature were given, and the coupling interaction mechanism between the hole subband transitions and the quantum-well LO phonon was researched.

RESEARCH ON COUPLED RELATIONSHIP BETWEEN HYDRATION NUMBER WITH RAMAN SPECTRUM

As we know, there are three structures-sⅠ, sⅡ, and sH, with hydrocarbonate gas hydrate.Because of those special structures characteristics and potentail large fossil energy resource, gas hydrate play an important role in natural carbonate cycle system. In this paper, CH4, CO2, C3H8, and CH4 +CO2 system have been experimental performed in order to model hydrate formation and discomposition and to obtain hydrate stability conditions of tempreature and pressure. The results from laboratory using Raman spectra show that Raman spectrascopy is a effective tool to identify hydrate structure. Raman spectra of clathrate hydrate guest molecules are presented for two structure (sⅠ and sⅡ) in the following systems: CH4, CO2, C3 H8. Relatively occupancy of CH4 in the large and small cavities of sⅠ were determined by deconvoluting the v1 symmetric bands, resulting in hydration numbers of 6.04±0.03. The freqyuency of the v1 bands for CH4 in structures Ⅰ and Ⅱ differ statistically. The large cavities were measured to be almost fully occupied by CH4 and CO2, whereas only a small fraction of the small cavities are occupied by CH4. No CO2 was found in the small cavities.

Low Temperature Preparation and Characterization for PbTiO_3 Ceramics by Sol-Gel Technique

This Paper reports a new system for preparation of lead titanate powders by the Sol Gel method. In this system, basic lead lactate, (CH 3CHOHCOO) 2Pb, is used as the lead precursor instead of the widely used Pb(OOCCH 3) 2·3H 2O and titanium tetrabutoxide monomer. This new system simplifies the chemical processing of precursor solutions of lead titanate, increases their stability in air, and offers good control Pb(Ti stoichiometry. The xerogel, obtained from the precursor solution by aging at low temperature, is found to have a higer inorganic content. Gel to ceramic conversion is achieved by calcining the xerogel from 400℃ to 800℃. The phase purity, particle size, morphology, compositional homogeneity of the gel derived powders are examined by XRD. TEM.IR and the slow reflection spectrum of partides are measured.

Improvement of Raman spectrum uniformity of SERS substrate based on flat electrode

The distribution of metal nanoparticles on the surface of a surface enhancement Raman scattering(SERS)-active substrate plays a prominent part in not only the enhancement of Raman vibration signal,but also the spectrum uniformity.Here,a facile method to fabricate SERS substrates with excellent homogeneity and low cost was proposed,in which a lyotropic liquid crystal soft template was introduced for the coordinated growth of the silver nanoflowers in the process of electrochemistry deposition.Simulation was carried out to illustrate the dominated influence of the distance of electrodes on the deposited nanoparticle number.Two kinds of conductive materials,silver plate and indium tin oxide(ITO)glass,were chosen as the anode,while the cathode was fixed as ITO glass.The simulated conjecture on the effect of electrode flatness on the uniformity of deposited nanoparticles in silver is experimentally proved.More importantly,it was demonstrated that with a relatively smooth and flat ITO glass anode,a SERS substrate featuring higher spectrum uniformity could be achieved.This work is of great significance to the actual applications of the SERS substrate for quantitative detection with high sensitivity.

A Study on the Raman Spectrum of the LiNbO_3－doped Mg Crystal at Low Temperature

The Raman Spectra of LiNbO3:MgO(6.7mol%) at both lowtemperature and room temperature were studied. The results showed that the crystal structure had changed little after doping Mg++. At room temperature the lattice distorted a litlte, which caused the appearance of couping phenomenon of some individual scattering peaks. As the temperature decreased, the coupling reduced gradually.

Exploring impedance spectrum for lithium-ion batteries diagnosis and prognosis:A comprehensive review

Lithium-ion batteries have extensive usage in various energy storage needs,owing to their notable benefits of high energy density and long lifespan.The monitoring of battery states and failure identification are indispensable for guaranteeing the secure and optimal functionality of the batteries.The impedance spectrum has garnered growing interest due to its ability to provide a valuable understanding of material characteristics and electrochemical processes.To inspire further progress in the investigation and application of the battery impedance spectrum,this paper provides a comprehensive review of the determination and utilization of the impedance spectrum.The sources of impedance inaccuracies are systematically analyzed in terms of frequency response characteristics.The applicability of utilizing diverse impedance features for the diagnosis and prognosis of batteries is further elaborated.Finally,challenges and prospects for future research are discussed.

A research on the effect of plasma spectrum collection device on LIBS spectral intensity

Only a small amount of spectral information is collected because the collection solid angle of the optical fiber probe and lens is very limited when collecting spectral information.To overcome this limitation,this study presents a novel method for acquiring plasma spectral information from various spatial directions.A parabolic-shaped plasma spectral collection device(PSCD)is employed to effectively collect more spectral information into the spectrometer,thereby enhancing the overall spectral intensity.The research objects in this study were soil samples containing different concentrations of heavy metals Pb,Cr,and Cd.The results indicate that the PSCD significantly enhances the spectral signal,with an enhancement rate of up to 45%.Moreover,the signal-to-noise ratio also increases by as much as 36%.Simultaneously,when compared to the absence of a device,it is found that there is no significant variation in plasma temperature when the PSCD is utilized.This observation eliminates the impact of the spatial effect caused by the PSCD on the spectral intensity.Consequently,a concentrationspectral intensity relationship curve is established under the PSCD.The results revealed that the linear fitting R^(2)for Pb,Cr,and Cd increased by 0.011,0.001,and 0.054,respectively.Additionally,the limit of detection(LOD)decreased by 0.361 ppm,0.901 ppm,and 0.602 ppm,respectively.These findings indicate that the spectral enhancement rate elevates with the increase in heavy metal concentration.Hence,the PSCD can effectively enhance the spectral intensity and reduce the detection limit of heavy metals in soil.

New Insight to the Surface Temperature of the Sun

Information is given on thermal radiation from the Sun, considered in practical engineering calculations of heat exchange. It was found that although the surface temperature of the Sun is assumed to be about 5800 K, the solar spectrum data measured by Kondratyev lead to a value of at least 7134 K. Such a higher value can be obtained by interpreting the Planck formula for the black radiation spectrum for the Kondratyev data. In addition, using the Stefan-Boltzmann law, the energetic emissivity of the Sun’s surface was determined to be 0.431. Furthermore, based on Petela’s formulae for exergy of thermal radiation, the exergetic emissivity of the Sun’s surface was also calculated at the level of 0.426.

Crystal Structure and Raman Spectrum of Neodymium（Ⅲ） Complex of p－Aminobenzoic Acid and 1，10－Phenanthroline

Crystal structure of tetra(1,10-Phenanthroline)neodymium (Ⅲ) tetra(4-aminobenzoate)-hydrate, [Nd(p-ABA)4·2Phen]H+3O·2Phen (p-ABA:p-aminobenzoate,Phen:1,10-phenanthroline) has been determined by X-ray diffraction.The complex crystallizes in monoclinic, space group C2/c.The cell dimensions are a=1.9067 (5) nm,b=1.9192 (3) nm,c=2.0190 (4) nm,β=117.25 (2) °.V=6.568 (3) nm3, Mr= 1428.63,Z=4 and Dx= 1.45 g·cm-3.The coordination number of Nd atom is 10, and the coordinated polyhedron around the Nd atom is distorted trigonal prism.

Raman Spectrum of Rhombohedral Neodymium-Aluminum Borate

The Raman spectrum of rhombohedral NdAl 3 (BO 3) 4 (NAB) is recorded and interpreted. A factor group analysis of the NAB space group shows that there are 21A 1 and 59E Raman active modes. A discussion of the assignment of the individual Raman lines is given. The splitting predicted by factor group for the internal modes of (BO 3) 3+ anion are observed and interpreted.

Si@Cu@Au AFM tips for tip-enhanced Raman spectrum

Tip-enhanced Raman spectrum(TERS) is a scanning probe technique for acquiring chemical information at high spatial resolution and with high chemical sensitivity. The sensitivity of TERS with atomic force microscopy(AFM) system is mainly determined by the metalized tips. Here, we report a fabrication protocol for AFM-TERS tips that incorporate a copper(Cu) primer film between a gold(Au) layer and a Si AFM tip. They were fabricated by coating the Si tip with a 2 nm Cu layer prior to adding a 20 nm Au layer. For top illumination TERS experiments, these tips exhibited superior TERS performance relative to that observed for tips coated with Au only. Samples included graphene, thiophenol and brilliant cresyl blue. The results may derive from the surface roughness of the tip apex and a Cu/Au synergism of local surface plasmon resonances.

Raman Scattering Spectrum Analysis of GaP andIts Luminous Materialsr

Abstract: The Raman scattering spectra of n- type GaP(doped S) single crystal and red and green luminous materials grown on the n - type GaP (doped S) single crys-tal substrate by liquid - phase epitaxy are analyed. The results show that the spectra of GaP single crystal and its luminous materials include not only the first - order longitudi-nal optical photons and transverse optical phonons Raman scattering peaks, but also the peaks of the bound excitons, bound electrons and bound holes.

In situ Detection of Amide A Bands of Proteins in Water by Raman Ratio Spectrum

The amide A band of protein is sensitive to the hydrogen bands of amide groups of proteins. However, it is hard to distinguish the amide A band of aqueous protein in situ directly, since it overlaps with O-H stretching vibration of water. In this work, we presented a new analytical method of Raman ratio spectrum, which can extract the amide A band of proteins in water. To obtain the Raman ratio spectrum, the Raman spectrum of aqueous protein was divided by that of pure water. A mathematical simulation was employed to examine whether Raman ratio spectrum is effective. Two kinds of protein, lysozyme and （^-chymotrypsin were employed. The amide A bands of them in water were extracted from Raman ratio spectra. Additionally, the process of thermal denaturation of lysozyme was detected from Raman ratio spectrum. These results demonstrated the Raman ratio spectra could be employed to study the amide A modes of proteins in water.

Fiber-Optic Raman Spectrum Sensor for Fast Diagnosis of Esophageal Cancer

A fiber-optic Raman spectrum sensor system is used for the fast diagnosis of esophageal cancer during clinical endoscopic examination.The system contains a 785nm exciting laser,a Raman fiber-optic probe with 7 large core fibers and a focus lens,and a highly sensitive spectrum meter.The Raman spectrum of the tissue could be obtained within 1 second by using such a system. A signal baseline removal and denoising technology is used to improve the signal quality.A novel signal feature extraction method for differentiating the normal and esophageal cancer tissues is proposed,based on the differences in half-height width(HHW)in 1200cm^-1 to 1400cm^-1 frequency band and the ratios of the spectral integral energy between 1600cm^-1-1700cm^-1 and 1500cm^-1- 1600cm^-1 band.It shows a high specificity and effectivity for the diagnosis of esophageal cancer.

Performance Improvements in Raman Distributed Temperature Sensor

The fiber optic distributed temperature sensor （DTS） is one of the most outstanding means to measure temperature distribution along an optical fiber. In this paper, we propose a novel calibration technique to measure the temperature highly accurately over a wide range of temperatures. We also propose an improved double-ended configuration that is insusceptible to the differential loss change in the fiber and suitable for the field use. Then, we developed an interrogator that had high robustness in harsh environments.

Channel temperature determination of a multifinger AlGaN/GaN high electron mobility transistor using a micro-Raman technique

Self-heating in a multifinger A1GaN/GaN high electron mobility transistor （HEMT） is investigated by micro-Raman spectroscopy, The device temperature is probed on the die as a function of applied bias. The operating temperature of the A1GaN/GaN HEMT is estimated from the calibration curve of a passively heated A1GaN/GaN structure. A linear increase of junction temperature is observed when direct current dissipated power is increased. When the power dissipation is 12.75 W at a drain voltage of 15 V, a peak temperature of 69.1 ℃ is observed at the gate edge on the drain side of the central finger. The position of the highest temperature corresponds to the high-field region at the gate edge.

Temperature Dependence of Raman Scattering in 4H-SiC Films under Different Growth Conditions

The microRaman scattering of 4H-SiC films, fabricated by low pressure chemical vapor deposition under different growth conditions, is investigated at temperatures ranging from 80 K to 550K. The effects of growth conditions on E2 （TO）, E1 （TO） and A1 （LO） phonon mode frequencies are negligible. The temperature dependences of phonon linewidth and lifetime of E2 （TO） modes are analyzed in terms of an anharmonic damping effect induced by thermal and growth conditions. The results show that the lifetime of E2 （TO） mode increases when the quality of the sample improves. Unlike other phone modes, Raman shift of A1 （longitudinal optical plasma coupling （LOPC）） mode does not decrease monotonously when the temperature increases, but tends to blueshift at low temperatures and to redshift at relatively high temperatures. Theoretical analyses are given for the abnormal phenomena of A1 （LOPC） mode in 4H-SiC.

Calculating the electron temperature in the lightning channel by continuous spectrum

Based on the theory of plasma continuous radiation, the relationship between the emission intensity of bremsstrahlung and recombination radiation and the plasma electron temperature is obtained. During the development process of a return stroke of ground flash, the intensity of continuous radiation spectrum is separated on the basis of the spectrums with obviously different luminous intensity at two moments. The electron temperature of the lightning discharge channel is obtained through the curve fitting of the continuous spectrum intensity. It is found that electron temperature increases with the increase of wavelength and begins to reduce after the peak. The peak temperature of the two spectra is close to 25 000 K. To be compared with the result of discrete spectrum, the electron temperature is fitted by the O I line and N II line of the spectrum respectively. The comparison shows that the high temperature value is in good agreement with the temperature of the lightning core current channel obtained from the ion line information, and the low temperature at the high band closes to the calculation result of the atomic line, at a low band is lower than the calculation of the atomic line, which reflects the temperature of the luminous channel of the outer corona.