类胡萝卜素的分子光谱研究

类胡萝卜素是含有9个CC共轭双键的短链多烯类生物分子. 特殊的分子结构, 使其不仅在光采集, 光防护, 防癌, 抗癌等生物学领域有重要应用, 而且在分子导线, 光开关, 滤光器等光电器件研制中也有重要的非生物学应用. 本文对它的分子光谱进行研究和总结, 结果表明, 类胡萝卜素具有宽带荧光, 将其用于荧光增强受激拉曼散射可以获得宽带受激拉曼散射; 电子能隙随温度降低而收缩, 电子吸收光谱红移, 这特性使它能研制优质半导体元件; 极大的拉曼活性和三阶非线性系数, CC键基频拉曼散射截面可以比普通分子大10个数量级, 和频、倍频拉曼散射强度也很高, 低温下与基频强度比可达0.5. 类胡萝卜素分子的这些光谱特性对多烯类分子结构、性能研究及其在非生物学中的应用有重要参数价值.     

Quasi-Elastic Light Scattering in Congruent Lithium Niobate Crystals

Raman scattering spectra in the frequency range of 5–75 cm^–1 in lithium niobate samples with various structural imperfections were obtained. It is shown that the intensity of quasi-elastic light scattering on the wing of the Rayleigh line demonstrates an exponential dependence on the concentration of large-scale defects in the samples. Calibration curves for the intensity of quasi-elastic scattering dependence at low frequencies on the acoustic quality factor are constructed.     

Stilbazolium merocyanine dye determination in different solutions,concentrations and colloids using SERS

Surface‐enhanced Raman scattering (SERS) measurements were carried out on stilbazolium merocyanine dye in methanol and pyridine solvents. Both solutions were measured in a series of concentrations covering a range of 5 × 10⁻⁵ M to 5 × 10⁻⁸ M . In these measurements, Ag and Au colloids were used, and the results have shown that Ag colloids yield better enhancement in the Raman spectra of this dye. Moreover, the effect of adding NaCl solution to the SERS samples was also studied. All measurements were carried out using the state‐of‐the‐art ChiralRaman instrument, which utilizes a 532 nm laser source. We report here on the success of using SERS to obtain Raman spectra of merocyanine dye at very low concentrations in an attempt to find a new approach that can be used for further investigations of the dye. The SERS spectra are reported here, and the results from different solutions, colloids, concentrations and pH values are compared. Copyright © 2006 John Wiley & Sons, Ltd.     

Light scattering evidence of a central component in ice Ih

High resolution Raman spectra of ice I_h single crystal in the frequency range 0–30 cm^?1 are reported, at various temperatures. For the first time evidence is given for the existence of a Lorentzian central component in all scattering configurations. A polarization analysis of the spectra clearly shows that the central mode cannot be ascribed to the high frequency tails of the Brillouin doublet, nor to the disorder induced phonon background even accounting for renormalization of the phonon propagator. The epectral features indicate the existence of a direct coupling between the light and some relaxation mechanism of the crystal.A model is suggested to account for the excess scattering and for the activation of the acoustic phonon density of states.     

强激光照射下,α-LiIO3晶体中晶格振动的多模激发和模之间的相互作用

本文叙述了用调Q倍频YAG脉冲激光照射α-LiIO₃晶体,在不同的散射配置下,获得了各种散射谱图。实验表明,当用e光入射时,可以比用o光入射激发起更多不同模的晶格振动;获得了E₂模的很强的一阶、二阶斯托克斯散射线和反斯托克斯散射线,E₁模Polariton的一阶、二阶、三阶斯托克斯线和反斯托克斯线,还获得了反斯托克斯频率区一条频移为469cm^-1的新线,认为是不同模的Polariton之间的相互作用引起的。最后,提到实验中初步观察到的晶体拉曼活性的“疲劳现象”。 关键词：     

一种用多色光作为激发源产生拉曼光谱的新算法

探讨用多色光代替激光作为拉曼光源的新型拉曼光谱仪的可能性。根据拉曼光谱原理, 并通过数学分析, 发现当用多色光照射在样品上时, 所得到的散射光经散射频率校正后在不同频率上的强度分布可以写成样品的Raman-Rayleigh联合散射谱和激发光光源的功率谱的卷积。利用傅里叶变换算法,有可能从多色光照射样品所得到的散射光谱中导出样品的拉曼光谱。基于上述原理,可能发展出不用激光的新一代拉曼光谱仪。     

Temperature dependence of anomalous and ordinary Raman scattering in β-AgI

We report careful measurements of the temperature dependence of Raman scattering in β-AgI, with particular emphasis on the region 12°K to 150°K. Our main result is that the anomalous features in the Raman spectra of β-AgI are definitely first order. Furthermore from the temperature dependence of the anomalous scattering intensity we infer the possibility of a first partial disordering in the Ag⁺ sublattice at about 50°K.     

Origin of the forbidden phonons in Raman scattering spectra of uranium‐doped Ca2CuO3, a spin 1/2 chain system

The Raman scattering spectra of uranium‐doped Ca₂CuO₃ were investigated. The small doping of uranium (≤5%) in this one‐dimensional spin 1/2 chain system induced three new first‐order scattering bands and two new multiphonon bands in the structure of forbidden phonons. The first‐order bands were found to agree well with the existing theoretical results from the ab initio and tight‐binding calculation. Among them, the 470 and 665 cm⁻¹ bands appeared as the basic wavenumbers of which the multiphonon overtones were composed. The grain size effect in this strongly anisotropic system was proposed not to originate from the classical phonon confinement but rather as a result of the segmentation of one‐dimensional spin chains due to doping, which in turn allowed the new vibrational modes and implied the appearance of higher overtones in the scattering spectra. Copyright © 2008 John Wiley & Sons, Ltd.     

Structural modifications of GaN after cerium implantation

Among the family of rare earth (RE) dopants, the doping of first member Ce into GaN is the least studied system. This article reports structure properties of Ce‐doped GaN realized by technique of ion implantation. Ce ions were implanted into metal organic chemical vapor deposition grown n‐ and p‐GaN/sapphire thin films at doses 3 × 10¹⁴ and 2 × 10¹⁵ cm⁻². X‐ray diffraction scans and Raman scattering measurements exhibited expansion of lattice in the implanted portion of the samples. First order Raman scattering spectra show appearance of several disorder‐activated Raman scattering modes in addition to typical GaN features. A dose‐dependent decrease in intensity of E₂ mode was observed in Raman the spectra of the implanted samples. Ultraviolet Raman spectra of implanted samples show complete quenching of photoluminescence emission and appearance of multiple A₁(LO) phonon scattering modes up to fifth order. Moreover, a decrease in intensity and an increase in line width of LO modes as a function of wavenumber were observed for implanted samples. Copyright © 2012 John Wiley & Sons, Ltd.     

密度泛函理论研究黄曲霉素B1的表面增强拉曼散射效应

用密度泛函理论B3LYP方法和6-311G(d,p)/Lanl2DZ优化得到黄曲霉素B₁(AFB₁)分子及其复合物AFB₁-Ag的稳定结构,并计算了复合物的表面增强拉曼光谱和预共振拉曼光谱. 结果表明,AFB₁分子的拉曼光谱很大程度依赖于吸附位点以及入射光的激发波长. 与分子的常规拉曼光谱相比,复合物表面增强拉曼光谱中C=O伸缩振动模的增强因子约为10²～10³复合物的极化率增强而导致的静态化学增强,并分析了振动模式的振动方向与其拉曼强度的关系．选择复合物最大吸收峰附近激发光266和482 nm以及远离共振吸收波长785和1064 nm作为入射光,计算得到不同入射光激发下复合物的预共振拉曼光谱．结果表明其增强因子最大达到10⁴量级,主要是由电荷转移产生的共振增强引起的．     

Dynamics of F2 centers in LiF: One phonon sideband and Raman scattering

The vibrational structure of the F₂⁺ emission in LiF was investigated, together with the resonant Raman scattering from the first excited electronic state. The one phonon sideband of the emission and the resonant Raman spectrum were found to be very similar, as expected for transitions involving non degenerate electronic states.     

BaTiO3和Ce:BaTiO3单晶的高温喇曼散射研究

从室温至180℃测量了BaTiO₃和Ce:BaTiO₃单晶的偏振喇曼谱,在X(ZZ)Y几何配置下发现了三条频率分别为986,1204和1480cm^-1的新谱线.根据喇曼散射截面的温度依赖关系,确认这些新谱线对应二阶喇曼散射,而A₁(TO)谱中位于275和514cm^-1处的非对称宽峰则属于一阶喇曼散射.在此基础上,对立方相BaTiO₃的喇曼谱和结构相变机制进行了讨论.通过比较B     

Rapid shifted excitation Raman difference spectroscopy with a distributed feedback diode laser emitting at 785 nm

A distributed feedback (DFB) laser diode emitting at 785 nm was tested and applied as a light source for shifted excitation Raman difference spectroscopy (SERDS). Due to the physical properties of the laser diode, it was possible to shift the emission wavelength by 8 cm^-1 (0.5 nm) required for our SERDS measurements by simply changing the injection current. The internal grating ensured single mode operation at both wavelength with the frequency stability of ±0.06 cm^-1 (0.004 nm) required for high resolution Raman spectroscopic applications. The shifted spectra were used for calculating enhanced Raman spectra being obscured by a strong scattering background. A 16 dB (≈38 fold) improvement of the signal-to-background noise S̄/σ_B was demonstrated using blackboard chalk as a sample. The tunable DFB laser is a versatile excitation source for SERDS, which could be used in any dispersive Raman system to subtract fluorescence contributions and scattering background. PACS 82.80.Gk; 42.55.-f; 42.64.Fi     

共振拉曼效应和电子-声子耦合对线性多烯分子共振拉曼光谱的影响

线性多烯分子具有高强度且信息丰富的共振拉曼光谱,在生物学、光电材料和医学等方面都有一定应用.而含有共轭双键的短链β胡萝卜素分子是多烯分子中极具有代表性的分子.在激发光作用下π电子与CC键振动相互作用影响着吸收光谱和拉曼光谱,而共振拉曼效应和电子-声子耦合影响着共振拉曼光谱的强度、频率和线型.测量了β胡罗卜素分子在二氯乙...     

Antiferroelectric and ferroelectric phase transitions of the displacive and order-disorder type in PbZrO3 and PbZr1-xTi x O3 single crystals

For PbZrO₃ and PbZr_0.99Ti_0.01O₃ single crystals the first order Raman light scattering spectra in the paraelectric phase have been analysed. In lead zirconate two kinds of crystals, with and without a transient phase, were investigated. It was found that temperature dependence of the defect-induced soft mode frequency in the paraelectric phase has a negligible contribution to the low-frequency dielectric response. From the point of view of strong dielectric relaxation in the range of 10⁶–10⁹ Hz, which originates in a disorder of the lead sites, crossover of the order-disorder and displacive type of antiferroelectric phase transition in lead zirconate is considered: the phase transition mechanism is neither purely displacive nor order-disorder. Contribution of physical phenomena responsible for the ε(ω,T) dielectric response at low frequencies of an external electric field are described.     

The Effect of L-Cysteine on Surface-Enhanced Raman Scattering of Malachite Green in Silver Colloids

ABSTRACT

Colloidal silver nanoparticles were prepared by a simple chemical reduction method. The effect of L-cysteine on the surface-enhanced Raman scattering activity of colloidal silver nanoparticles was investigated by using malachite green as a probe molecule. It was found that the surface-enhanced Raman scattering activity of colloidal silver nanoparticles was improved tremendously with the help of L-cysteine. The possible reasons for this enhancement effect were given. Specifically, in silver colloidal solution, no surface-enhanced Raman scattering spectrum of malachite green was observed at a relatively low concentration (≤2.5 × 10^?5 mol/L). However, well-resolved and high-quality surface-enhanced Raman scattering spectra of malachite green were successfully obtained after the addition of L-cysteine to silver colloids, and the minimum detection limit for malachite green was down to 10^?8 mol/L.     

Quantized infrared-optical triple resonance on a single cold barium ion

A single trapped and cooled Ba⁺ ion is irradiated by resonant visible light (493, 650 nm) alternating with light at 1.76 µm which may excite the ion to its² D _5/2 metastable state. The (absence of) visible resonance scattering probes the excitation, tuning spectra of which show vibrational sidebands that characterize the ion's temperature. Observed values as low as 120 µK, one-eighth the Doppler limit, are ascribed to electronic Raman cooling by the visible light. Tuning spectra of the events of stimulated deexcitation indicate ion heating by the IR interaction. The results demonstrate the feasibility of vibrational spectrometry on a single particle that oscillates in a potential well, forming a quasi-molecule.     

Orthorhombic lutetium germanate NaLuGeO<Subscript>4</Subscript>: A new SRS-active crystal

The discovery of the effect of simulated Raman scattering in the NaLuGeO₄ rhombic crystal and the first results of studying the spectra of two-phonon steady χ⁽³⁾ nonlinear picosecond lasing are reported.     

Characterization of three-color CARS in a two-pulse broadband CARS spectrum

We demonstrate that a broadband coherent anti-Stokes Raman scattering (CARS) spectrum generated with a typical two-pulse scheme contains two distinct, significant signals: '2-color' CARS, where the pump and probe are provided by a narrowband pulse and the continuum pulse constitutes the Stokes light, and '3-color' CARS, where the pump and Stokes are provided by two different frequency components in the continuum pulse and the narrowband pulse serves as the probe. The CARS spectra from the two different mechanisms show distinct characteristics in Raman shift range, laser power dependence, and chirping dependence. We discuss the potential for a 3-color CARS signal to cover the fingerprint region with reduced photodamage of live cells. Official contribution of the National Institute of Standards and Technology; not subject to copyright in the United States.     

Magneto-Raman scattering inp-type indium antimonide

We report for the first time stimulated magneto-Raman scattering inp-type InSb. Two different Raman scattering processes were observed. The first one has a Raman shift of about 2cm⁻¹/kG and is observed at magnetic fields up to 30kG. The other one is observable only at high magnetic fields above 30kG and shows Raman shifts between 1.2cm⁻¹ and 3.0cm⁻¹ with a tuning rate of about 0.2cm⁻¹/kG. The first process can be interpreted either as spin-flip Raman scattering by photo-excited electrons in the conduction band or as Raman scattering by holes in the valence band involving transitions from heavy to light hole states. The other Raman shift observed seems to occur on account of transitions between the heavy hole ladders.