Influence of the ordered structure of short-chain polymer molecule all-trans-β-carotene on Raman scattering cross section in liquid

We measured the resonant Raman spectra of all-trans-β-carotene in solvents with different densities and concentrations at different temperatures.The results demonstrated that the Raman scattering cross section(RSCS) of short-chain polymer all-trans-β-carotene is extremely high in liquid.Resonance and strong coherent weakly damped CC bond vibrating properties play important roles under these conditions.Coherent weakly damped CC bond vibration strength is associated with molecular ordered structure.All-trans-β-carotene has highly ordered structure and strong coherent weakly damped CC bond vibrating properties,which lead to large RSCS in the solvent with large density and low concentration at low temperature.     

Study of second-order nonlinear hyperpolarisability of all-trans-β-carotene in solutions by linear spectroscopic technique

This paper demonstrates the second-order nonlinear hyperpolarisability \gamma of all-trans-β-carotene in different solvents by linear spectroscopic technique that is based on resonance Raman scattering and UV--VIS (Ultraviolet-visible) absorption spectroscopy. Owing to the two-level model well describing the link that exists between the resonance Raman scattering and stimulated Raman scattering, the stimulated Raman polarisability α_{\rm R} can be calculated through the two-photon resonance system. The value of \gamma of all-trans-β-carotene in carbon bisulfide solution is 6.435\times 10^{-33} esu (1~esu of resistance =8.98755\times10^{11}~\Omega) that is close to the true value, because the solution of all-trans-β-carotene in carbon bisulfide satisfies the rigid resonance Raman scattering condition. This method is expected to be worthy of applications to measure the second-order nonlinear hyperpolarisability of a conjugate organic molecule.     

Effect of solution concentration on the structured order and optical properties of short-chain polyene biomolecules

We have measured the Raman spectra and UV-Vis absorption spectra of linear polyene biomolecules(β-carotene and lycopene) in CS2 at low concentrations(10-6-10-10 mol/L).With decreasing concentration,all the carbon-carbon vibrations form a coherent mode in ordered β-carotene and lycopene due to extended π-conjugation that gives strong electron-phonon coupling,which leads to an anomalous experimental phenomenon.We observed an extremely high Raman scattering cross section(RSCS) and the Raman activities in β-carotene and lycopene are characterized by intensive overtones and combinations.Further,the UV-Vis absorption bands become narrower.     

Ahnormal Crystallization of Silicon Thin Films Deposited by ICP-CVD

Silicon thin films are deposited by inductively coupled plasma chemical vapour deposition （ICP-CVD） at a low temperature of 350℃ using a mixture of SiH4 and H2. The structures of the films are characterized by x-ray diffraction and Raman spectra. Under the optimum experimental conditions, we observe that the crystallinity of Si films becomes more excellent and the preferred orientation changes from （111） to （220） with the decreasing dilution of SiH4 in H2. Such an abnormal crystallization is tentatively interpreted in term of the high density, low electron temperature and spatial confinement of the plasma in the process of ICP-CVD.     

Vibrational Energy—Spectra and Infraned Absorption of α—Helical Protein Molecules

The quantum energy spectran,including high excited states,of vibrational amide-I or of intramolecular excitations in α-helical protein molecules,are calculated by the discrete nonlinear Schrodinger equation together with the parameters appropriate to the systems.The distribution of energy levels obtained is basically consistent with the experimental values obtained by infrared absorption and Raman scattering.Utilizing the energy spectra we explain the laser Raman spectrum from metabolically active escherichia coli and we present some further features of the infrared absorption of the protein molecules.     

Surface-enhanced Raman spectroscopy of morphine in silver colloid

We report the surface-enhanced Raman （SERS） spectra of morphine in silver colloid, and study the silver colloid enhanced effects on the Raman scattering of morphine. The Raman bands of morphine are assigned to certain molecule vibrations. The broad band in the long-wavelength region of the electronic absorption spectra of the sol with added adsorbent at certain concentrations has been explained in terms of the ag- gregation of the colloidal silver particles. The potential applications of SERS in quantitative measurement of the morphine samples are demonstrated. By using a proper Raman band of morphine, the detection limit of morphine in silver sol is found to be 1.5 ng/ml. The result suggests that it is of great significance to use SERS in illicit drug morphine inspection.     

Effect of Pressure on Absorption Spectra of Lycopene in n-Hexane and CS2 Solvents

The absorption spectra of lycopene in n-hexane and CS2 are measured under high pressure and the results are compared with β-carotene. In the lower pressure range, the deviation from the linear dependence on the Bayliss parameter （BP） for β-carotene is more visible than that for lycopene. With the further increase of the solvent BP, the 0-0 bands of lycopene and β-carotene red shift at almost the same rate in n-hexane; however, the 0-0 band of lycopene red shifts slower than that of β-carotene in CS2. The origins of these diversities are discussed taking into account the dispersion interactions and structures of solute and solvent molecules.     

Temperature-dependent far-infrared properties of Bi12GeO20 single crystal

Far-infrared reflectivity spectra of bismuth germanium oxide (Bi12GeO20) single crystals are measured from room temperature down to 10 K. All the reflectivity spectra are fitted to a complex dielectric function ε(ω) in the factorised form. Phonon modes at low frequency are found to develop upon decreasing temperature and gain considerable spectrum weight below 150 K. The temperature-dependent static dielectric constants are obtained from the Lyddane-Sachs-Teller relation based on the obtained oscillator parameters. The dielectric constants are found to increase upon decreasing temperature, which is attributed to the charge transfer among the ions in the unit cell with the temperature varying.     

Electrical Properties and Raman Spectra of BaBi1-xPbxO3

Crystal structure, electrical properties and Raman spectra of BaBi1-xPbxO3 are reported. The result of x-ray diffraction shows that the specimen is pure, and the lattice parameters decrease continuously in the semiconducting range, whereas it vibrates similarly to a sine wave in the superconducting range, which is ascribed to the existence of oxygen vacancies and the function of breathing modes of Bi（Pb）O6. The temperature dependence of resistivity indicates that the electrical property of the samples is connected sensitively with the crystal structures. Raman spectra show that the specimen becomes disorder when x increases, and the critical temperature To depends not only on the deformation potential of the soft A19 mode derived from the Bi（Pb）O6 rigid rotation, but also on the energy shift of the mode.     

Raman scattering of polycrystalline GaSb thin films grownby co-evapouration process

<正>This paper reports that GaSb thin films have been co-deposited on soda-lime glass substrates.The GaSb thin film structural properties are characterized by Raman spectroscopy.The Sb-A_1g/GaSb-TO ratio decreases rapidly with the increase of substrate temperature,which suggests a small amount of crystalline Sb in the GaSb thin film and suggests that Sb atoms in the thin film decrease.In Raman spectra,the transverse optical（TO） mode intensity is stronger than that of the longitudinal optical（LO） mode,which indicates that all the samples are disordered.The LO/TO intensity ratio increases with increasing substrate temperature which suggests the improved polycrystalline quality of the GaSb thin film.A downshift of the TO and LO frequencies of the polycrystalline GaSb thin film to single crystalline bulk GaSb Raman spectra is also observed.The uniaxial stress in GaSb thin film is calculated and the value is around 1.0 GPa.The uniaxial stress decreases with increasing substrate temperature.These results suggest that a higher substrate temperature is beneficial in relaxing the stress in GaSb thin film.     

Temperature effect on emission lines and fluorescence lifetime of the ~4F_(3/2) state of Nd:YVO_4

By measuring the absorption and fluorescence spectra and the fluorescence lifetime of 4F3/2 state of Nd3+ ions in YVO4 (2 at.-%) crystal at different temperature, the effects of temperature on the spectra and the lifetime of F3/2 state have been investigated. As the temperature is increased, the line width of the 4F3/2 -4I11/2 transitions is found to increase and the spectral line toward the longer wavelength, which are duo to the ion-phonon interaction. The variation fluorescence lifetime of the 4F3/2 state of Nd:YVO4 is found to be anomalous in the measured range 8 - 300 K. It is about 81 us at room temperature and decreases to 30 us at 8 K. The experimental results are explained by ascribing to the thermal mixing between the two Stark levels of 4F3/2 state with different lifetime.     

Porosity Evaluation and the Power Spectral Densities Analyses of Carbon-Nickel Composite Films Annealed at Different Temperatures

The densification and the fractal dimensions of carbon-nickel films annealed at different temperatures 300,500,800,and 1000℃with emphasis on porosity evaluation are investigated.For this purpose,the refractive index of films is determined from transmittance spectra.Three different regimes are identified,T500℃,500℃T800℃and T800℃.The Rutherford backscattering spectra show that with increasing the annealing temperature,the concentration of nickel atoms into films decreases.It is shown that the effect of annealing temperatures for increasing films densification at T500℃and T800℃is greater than the effect of nickel concentrations.It is observed that the effect of decreasing nickel atoms into films at 500℃T800℃strongly causes improving porosity and decreasing densification.The fractal dimensions of carbon-nickel films annealed from 300 to 500℃are increased,while from 500 to 1000℃these characteristics are decreased.It can be seen that at 800℃,Elms have maximum values of porosity and roughness.     

Structural and electrical characterization of annealed Si1-xCx/SiC thin film prepared by magnetron sputtering

Si-rich Sil-xCx/SiC multilayer thin films are prepared using magnetron sputtering, subsequently followed by thermal annealing in the range of 800-1200 ℃. The influences of annealing temperature （Ta） on the formation of Si and/or SiC nanocrystals （NCs） and on the electrical characteristics of the multilayer film are investigated by using a variety of analytical techniques, including X-ray diffraction （XRD）, Raman spectroscopy and Fourier transform infrared spectrometry （FT-IR）, current-voltage （I-V） technique, and capacitance-voltage （C-V） technique. XRD and Raman analyses indicate that Si NCs begin to form in samples for Ta _ 800 ~C. At annealing temperatures of 1000 ℃ or higher, the formation of Si NCs is accompanied by the formation of SiC NCs. With the increase in the annealing temperature, the shift of FT-IR Si-C bond absorption spectra toward a higher wave number along with the change of band shape can be explained by a Si-C transitional phase between the loss of substitutional carbon and the formation of SiC precipitates and a precursor for the growth of SiC crystalline. The C-V and I-V results indicate that the interface quality of Si1-xCx/SiC multilayer film is improved significantly and the leakage current is reduced rapidly for Ta ≥ 1000 ℃, which can be ascribed to the formation of Si and SiC NCs.     

Nitrogen-Doped Chemical Vapour Deposited Diamond： a New Material for Room-Temperature Solid State Maser

Electron spin resonance （ESR） in polycrystalline diamond films grown by dc arc-jet and microwave plasma chemical vapour deposition is studied. The films with nitrogen impurity concentration up to 8 × 10^18 cm^-3 are also characterized by Raman, cathodoluminescence and optical absorption spectra. The ESR signal from P1 centre with g-factor of 2.0024 （nitrogen impurity atom occupying C site in diamond lattice） is found to exhibit an inversion with increasing the microwave power in an H102 resonator. The spin inversion effect could be of interest for further consideration of N-doped diamonds as a medium for masers operated at room temperature.     

Preparation and photoluminescence of nanowire array and films of cadmium sulfied by electrodepositing in organic solvent

Nanowir array and film of cadmium sulfide were prepared by eletroplating in organic solvent dimethyl sulfoxide with CdCl2 and element sulfur under different temperature and current density.The UV-VIS absorption spectra show that increasing the electroplating temperature is benefit to forming perfect crystallites of energy shift for the lowest sveral excitons is given and compared with th experiment.The photoluminescence spectrum consists of two parts:the first is produced by recombination of the defcets and the second by recombination of excitons.     

Optical fiber temperature sensor based on wavelength-dependent detection

Semiconductor fiber temperature sensors have been used widely in many fields, but most of them pick up temperature by measuring the optical intensity of certain fixed narrow-band in absorption spectrum. Furthermore,they are sensitive to the loss of optical intensity and the fluctuation of light source power. The novel temperature measurement system proposed in this paper is based on the semiconductor absorption theory and the spectral analysis of method.To measure temperature,the sensor model detects not the certain narrow-band spectrum but the most spectra of the optical absorption edge.Therefore the measurement accuracy and the stability can be improved greatly.Experimental results are in agreement with theoretical analysis results perfectly.     

Growth and optical properties of Cr~（3＋）-doped CdWO_4 single crystals

A high-quality Cr 3+:CdWO4 single crystal at a size of approximatelyΦ25×80 mm is grown using the Bridgman method with CdO,WO3,and Cr2O3 as raw materials and their molar ratio of 100:100:0.5.The temperature gradient of solid-liquid interface at growth is approximately 50?C/cm and the growth rate is 0.05 mm/h.The X-ray diffraction(XRD),absorption,excitation,and emission spectra of different parts of the as-grown and O2-annealed crystals are investigated.Two strong broad optical absorption bands of about 472 and 708 nm are observed,and they are associated with the transitions 4 A2→ 4 T1 and 4 A2→ 4 T2.The weak 4 T2→ 2 E transition(the R-line)at 632 nm is also observed.The crystal-field parameter Dq and the Racah parameters B and C are estimated to be 1 412.4,776.8,and 3 427.6 cm? 1,respectively,according to the absorption spectra and crystal-splitting theory.A broadband fluorescence at about 1 000 nm due to 4 T2→ 4 A2 transition is produced by exciting the samples at 675 nm.After being annealed in an O2 atmosphere,the crystals become more transparent,while the effective light absorption of Cr 3+ ions is evidently enhanced and the emission intensity is also strengthened due to the reduction of oxygen vacancies in the CdWO4 crystal after annealing.     

Structure and photoluminescence properties of Er3+-doped TiO2-SiO2 powders prepared by sol-gel method

Er 3+-doped TiO 2-SiO 2 powders are prepared by the sol-gel method,and they are characterized by high resolution transmission electron microscopy (HR-TEM),X-ray diffraction (XRD) spectra,and Raman spectra of the samples.It is shown that the TiO 2 nanocrystals are surrounded by an SiO 2 glass matrix.The photoluminescence (PL) spectra are recorded at room temperature.A strong green luminescence and less intense red emission are observed in the samples when they are excited at 325 nm.The intensity of the emission,which is related to the defect states,is strongest at the annealing temperature of 800 C.The PL intensity of Er 3+ ions increases with increasing Ti/Si ratio due to energy transfer between nano-TiO 2 particles and Er 3+ ions.     

First-principles studies of the vibrational properties of amorphous carbon nitrides

Raman spectra of amorphous carbon nitride films (a-C:N) resemble those of typical amorphous carbon (a-C), and no specific features in the spectra are shown due to N doping. The present work provides a correlation between the microstructure and vibrational properties of a-C:N films from first principles. The six periodic model structures of 64 atoms with various mass densities and nitrogen contents are generated by the liquid-quench method using Car-Parinello molecular dynamics. By using Raman coupling tensors calculated with the finite electric field method, Raman spectra are obtained. The calculated results show that the vibrations of C=N could directly contribute to the Raman spectrum. The similarity of the Raman line shapes of N-doped and N-free amorphous carbons is due to the overlapping of C=N and C=C vibration bands. In addition, the origin of characteristic Raman peaks is also given.     

Modeling the interaction of nitrate anions with ozone and atmospheric moisture

The molecular dynamics method is used to investigate the interaction between one–six nitrate anions and water clusters absorbing six ozone molecules. The infrared(IR) absorption and reflection spectra are reshaped significantly, and new peaks appear at Raman spectra due to the addition of ozone and nitrate anions to the disperse water system. After ozone and nitrate anions are captured, the average(in frequency) IR reflection coefficient of the water disperse system increased drastically and the absorption coefficient fell.