Double resonance Raman effects in InN nanowires

We study the excitation wavelength dependence of the Raman spectra of InN nanowires. The $ E_1 ({\rm LO})$ phonon mode, which is detected in backscattering configuration because of light entering through lateral faces, exhibits an upward fre‐ quency shift that can be explained by Martin's double resonance. The $ E_1 ({\rm LO})$ /$ E_2^h $ intensity ratio increases with the excitation wavelength more rapidly than the $A_1 ({\rm LO})/E_2^h $ ratio measured in InN thin films. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Raman scattering from one-dimensional carbon systems

Although the Raman effect was discovered nearly 80 years ago, it is only recently that the special characteristics of Raman scattering for one-dimensional systems have been seriously considered. This review focuses on the special interest of the Raman effect for one-dimensional systems that is of particular relevance to carbon nanostructures. Two examples of Raman scattering in one-dimensional systems are given. The first illustrates the use of Raman spectroscopy to reveal the remarkable structure and properties of carbon nanotubes arising from their one-dimensionality. Some of the recent advances in using Raman spectroscopy to study doping and intercalation to modify nanotube properties are reviewed, in the context of a one-dimensional system. The second example is the Raman spectra of a linear chain of carbon atoms and the special properties of this interesting system. New approaches toward applying Raman spectroscopy to carbon nanostructures are also emphasized.     

Surface-enhanced Raman scattering from the individual metallic single-walled carbon nanotubes

A new experimental technique has been presented to investigate the surface-enhanced Raman scattering (SERS) on “individual and untouched” single-walled carbon nanotubes (SWNTs) deposited onto gold or silver film-covered substrate through a direct CVD method. It was found that the radial breathing mode for SERS shows a narrower linewidth than the normal Raman spectroscopy (NRS). Relative to NRS, the SERS spectra also revealed a preferable contribution to some metallic component of the G line. However no obvious difference for D and G′ between SERS and NRS has been revealed, which is different from the previous results on bulk SWNT samples.     

铯原子介质中受激拉曼四波混频的光放大特性

实验研究了在铯原子介质中受激拉曼四波混频过程中,注入的探针光与所产生的共轭光的增益特性,具体比较了在探针场分别作为Stokes场和Anti-Stokes场情况下,增益随粒子数密度、泵浦光频率失谐的依赖关系,并分析了其增益谱线线型和谱宽.为进一步开展基于受激拉曼四波混频进行量子关联光束的制备提供了主要实验参数的选择参考.     

关于碳纳米管反常反斯托克斯拉曼(AASR)光谱现象的研究

在碳纳米管中观察到了反常反斯托克斯拉曼（ＡＡＳＲ）光谱现象,并发现ＡＡＳＲ现象与碳纳米管的管层数和碳材料的片层样结构无关,因而揣测它可能只与碳纳米管的管状结构有联系。     

钠分子的共振喇曼散射

本文用80mW6238.2(?)的He-Ne激光激发钠蒸气,用一种新颖的棱镜反射光路,从后向首次观察到了56O0～8200(?)钠分子的共振喇曼谱.     

LDS751染料的受激喇曼散射

报道了用532nm激光抽运LDS751染料产生720—780nm可调谐染料激光输出的同时,观察到喇曼频移为102和45cm-1的反斯托克斯线,前者谱线较强,后者较弱.与这两条强线对应的斯托克斯线未能观察到.另外,还观察到喇曼频移为34cm-1的一级和二级斯托克斯线与反斯托克斯线 关键词： LDS751染料 受激喇曼散射 喇曼位移 斯托克斯线 反斯托克斯线     

Aluminium nanohole arrays enhanced resonance Raman scattering spectra in the near ultraviolet region

Aluminium nanohole arrays with fixed diameter were fabricated by focused ion beam and the periodicities were turned.Aluminium nanohole arrays enhanced resonance Raman scattering spectra in the near ultraviolet region were studied experimentally and theoretically,which revealed that the SERRS enhancement factor was as high as 6 orders.     

Detection of invisible phonon modes in individual defect-free carbon nanotubes by gradient-field Raman scattering

We provide an effective method to investigate the field gradient effect in nanoconfined plasmon-matter interaction.Aligned ultralong SWNTs without defects were grown on marked substrates, followed by assembling gold nanoparticle clusters around individual nanotubes. The Raman scattering behavior of a nanotube placed in an atomic scale nanogap between adjacent nanoparticles was studied. In addition to the expected plasmon-induced Raman enhancement up to 103,the defect-free D-mode of an individual SWNT induced by gradient field is found for the first time. When the light is confined at atomic scale, gradient field Raman scattering becomes significant and dipole-forbidden phonon modes can be activated by quadrupole Raman tensor variation, indicating breakdown of the Raman selection rules.     

Pressure-tuned resonance Raman scattering and photoluminescence studies on MBE grown bulk GaAs at theE 0 gap

Hydrostatic pressure has been used to tune in resonance Raman scattering (RRS) in bulk GaAs. Using a diamond anvil cell, both the photoluminescence peak (PL) and the 2 LO and LO-phonon Raman scattered intensities have been monitored, to establish RRS conditions. When theE ₀ gap of GaAs matchesħω _S orħω _L, the 2 LO and LO-phonon intensity, respectively, exhibit resonance Raman scattering maxima, at pressures determined byħω _L. With 647.1 nm radiation (ħω _L = 1.916 eV), a sharp and narrow resonance peak at 3.75 GPa is observed for the 2 LO-phonon. At this pressure the 2 LO-phonon goes through its maximum intensity, and falls right on top of the PL peak, revealing thatħω _S(2 LO) =E ₀. This is the condition for “outgoing” resonance. Experiments with other excitation energies (ħω _L) show, that the 2 LO resonance peak-pressure moves to higher pressure with increasingħω _L, and the shift follows precisely theE ₀ gap. Thus, the 2 LO RRS is an excellent probe to follow theE ₀ gap, far beyond the Γ-X cross-over point. A brief discussion of the theoretical expression for resonance Raman cross section is given, and from this the possibility of a double resonance condition for the observed 2 LO resonance is suggested. The LO-phonon resonance occurs at a pressure whenħω _L ≈E ₀, but the pressure-induced transparency of the GaAs masks the true resonance profile.     

碳纳米管拉曼光谱研究新进展

本文介绍碳纳米管拉曼光谱研究的最新进展。重点介绍金属性和半导体性碳纳米管的共振拉曼效应、表面增强拉曼效应和偏振拉曼效应。同时也介绍了碳纳米管的温度效应、压力效应和杨氏模量的拉曼光谱研究     

Surface-enhanced resonance Raman scattering spectroscopy of single R6G molecules

Surface-enhanced resonance Raman scattering (SERRS) of Rhodamine 6G (R6G) adsorbed on colloidal silver clusters has been studied. Based on the great enhancement of the Raman signal and the quench of the fluorescence, the SERRS spectra of R6G were recorded for the samples of dye colloidal solution with different concentrations. Spectral inhomogeneity behaviours from single molecules in the dried sample films were observed with complementary evidences, such as spectral polarization, spectral diffusion, intensity fluctuation of vibrational lines and even ``breathing' of the molecules. Sequential spectra observed from a liquid sample with an average of 0.3 dye molecules in the probed volume exhibited the expected Poisson distribution for actually measuring 0, 1 or 2 molecules. Difference between the SERRS spectra of R6G excited by linearly and circularly polarized light were experimentally measured.     

Study of nonplanar distortions of Ni(II)-mesomethylporphyrins using spectroscopy of resonance Raman scattering

The role of mesomethyl substitution and of steric interaction of peripheral substituents in the formation of nonplanar distortions of the porphyrin macrocycle is studied for a series of Ni(II)-porphyrins. Resonance Raman spectra are recorded for Ni(II)-5-methyl-2,3,7,8,12,13,17,18-octaethylporphyrin (1); Ni(II)-2,5,8,12,18-pentamethyl-3,7,13,17-tetraethylporphyrin (2); and Ni(II)-3,5,7,12,17-pentamethyl-2,8,12,17-tetraethylporphyrin (3). The obtained spectra are compared with spectra of Ni-octaethylporphyrin (Ni-OEP) and Ni-etioporphyrin II. It is found that introducing one methyl group into a mesoposition leads to significant low-frequency distortions of the structure-sensitive lines of resonance Raman scattering. Specifically, frequenciesν ₃ ,ν ₁₁ ,ν ₁₉ ,ν ₂ , andν ₁₀ decrease by 10–44 cm⁻¹ while frequencyν ₄ remains practically unchanged. It is shown that the observed spectral variations are caused by nonplanar distortions of the structure of Ni-porphyrins. The same tendency of the line displacement for tetragonal Ni-OEP and for compounds 1, 2, and 3 indicates that CH₃-mesosubstituted Ni-porphyrins have a “corrugated” structure. The degree of nonplanarity is modulated by alkyl groups on pyrrole rings and increases in the porphyrin series 3→2→1. All mesomethyl-substituted Ni-porphyrins have spectral indications that the considered compounds are structurally heterogeneous in solution due to the presence of conformers with different degrees of planarity. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 170–176, March–April, 1999.     

用激光增益获取弱增益拉曼模式的受激拉曼散射光谱

当酒精的弱增益拉曼模式处于罗丹明640染料分子的激光增益范围时，在由悬垂液滴构成的圆形谐振腔中，观察到乙醇分子C—H伸缩系列模中多个弱增益拉曼模式的受激拉曼散射（SRS）光谱.随着抽运光的增强，迅速增长的强增益拉曼模式的受激辐射抑制了其他弱增益模式的SRS，并导致染料激光的完全淬灭.通过分析圆形腔腔模的光子速率方程和激光染料分子的三能级粒子数速率方程，解释了观察到的实验现象. 关键词： 受激拉曼散射 悬垂液滴 弱拉曼增益模式 激光增益     

n-SiC的电子拉曼散射及二级拉曼谱研究

研究了利用离子注入法得到的掺氮n-SiC拉曼光谱. 理论线形分析表明,与4H-SiC相比,6H-SiC中LO声子等离子体激元耦合模(LOPC模)拉曼位移随自由载流子浓度变化较小. 5145nm激发光下得到的电子拉曼散射光谱表明,k位处由1s(A₁)到1s(E)的能谷轨道跃迁带来的拉曼谱6H-SiC中有四条,4H-SiC中有二条;高频6303及635cm^-1处观察到的谱线被认为与深能级缺陷有关. 最后,利用纤锌矿型结构二级拉曼散射选择定则指认了6 关键词： 碳化硅 电子拉曼散射 轨道能谷分裂 倍频谱     

分子间费米共振增强二元溶液体系的受激拉曼散射研究

研究了液芯光纤内不同体积比的甲苯和间二甲苯二元混合溶液的受激拉曼散射.实验结果表明:在不同的体积比之下二元溶液的环呼吸振动模式1002 cm^-1,甲基的CH伸缩振动模式2920 cm^-1 以及芳香环CH对称伸缩振动模式3058 cm^-1的拉曼带同时产生受激拉曼辐射,并且2920 cm^-1 和 3058 cm^-1 拉曼带的一阶受激拉曼散射阈值要低于1002 cm^-1拉曼带的二阶 关键词： 分子间费米共振 二元溶液 受激拉曼散射 拉曼散射截面     

Enhancement of Raman scattering by individual dielectric microspheres

Enhanced Raman scattering (ERS) from bulk Si and surface brilliant cresyl blue (Bcb) molecules was investigated by individual polystyrene (PS) microspheres placed on top of the samples. It is revealed that the Raman signal depends both on the microsphere size and the numerical aperture (NA) of the collection lens, and a maximum signal enhancement of ∼11‐ and 40‐fold for Si and Bcb is observed, respectively, showing strong ERS effect. The different ERS behavior was elucidated by electromagnetic simulations using the finite element method. The present work also provides information on individual dielectric sphere for applications in microscopy, spectroscopic imaging and improvement, etc. Copyright © 2010 John Wiley & Sons, Ltd.     

硅酸盐熔体微结构单元的对称伸缩模的拉曼散射系数

通过一种新开发的模拟计算方法，计算了硅酸钠熔体的拉曼谱，及其在高频区代表5种硅氧 四面体(用Qi表示，其中i表示桥氧数)的特征峰的拉曼散射系数Si，发现成分的变化对5 种Qi的特征峰的拉曼散射系数的影响非常小.在此基础上取平均分别得到：S0=1,S1=0 ．514,S2=0242,S3=0090和S4=0015然后将计算得到的散射系数应用于二硅酸 钠熔体的实验谱图的定量分析中，得到了该熔体中硅氧四面体单元的分布.同时从计算与试 验谱图的定量解谱中发现，钠系硅酸盐熔体谱中Q0和Q2的ASS模所产生的散射信号 不容忽视. 关键词： 拉曼散射系数 硅氧四面体 硅酸盐熔体 高温拉曼谱     

采用圆偏振啁啾飞秒激光脉冲操控CS2分子的相干拉曼散射过程

采用两束圆偏振啁啾飞秒激光脉冲,非共线相干激发三原子分子CS₂液体. 在相位匹配的方向上,探测到由CS₂频率为397 cm^-1的振动模式产生的强度对称分布的相干反斯托克斯拉曼散射(CARS)信号和相干斯托克斯拉曼散射(CSRS)信号. 当调整两束激发光的圆偏振状态时,CARS,CSRS信号的强度、偏振、波长均发生规律性的改变:CARS,CSRS信号的强度分布反映了CS₂ 在不同极化状态下的受激拉曼散射截面大小;信号光的 关键词： 啁啾脉冲 相干反斯托克斯拉曼散射(CARS) 相干斯托克斯拉曼散射(CSRS) 2')" href="#">CS₂     

Changes in the vibrational modes of carbon nanotubes induced by electron‐beam irradiation: resonance Raman spectroscopy

Influence of electron‐beam (e‐beam) irradiation on multi‐walled (MW) and single‐walled (SW) carbon nanotube films grown by microwave chemical vapor deposition technique is investigated. These films were subjected to an e‐beam energy of 50 keV from a scanning electron microscope for 2.5, 5.5, 8.0, and 15 h, and to 100 and 200 keV from a transmission electron microscope for a few minutes to ∼2 h continuously. Such conditions resemble an increased temperature and pressure regime enabling a degree of structural fluidity. To assess structural modifications, they were analyzed prior to and after irradiation using resonance Raman spectroscopy (RRS) in addition to in situ monitoring by electron microscopy. The experiments showed that with extended exposures, both types of nanotubes displayed various local structural instabilities including pinching, graphitization/amorphization, and formation of an intramolecular junction (IMJ) within the area of electron beam focus possibly through amorphous carbon aggregates. RRS revealed that irradiation generated defects in the lattice as quantified through (1) variation of the intensity of radial breathing mode (RBM), (2) intensity ratio of D to G band (I_D/I_G), and (3) positions of the D and G bands and their harmonics (D* and G*) and combination bands (D + G). The increase in the defect‐induced D band intensity, quenching of RBM intensity, and only a slight increase in G band intensity are some of the implications. The MW nanotubes tend to reach a state of saturation for prolonged exposures, while the SW ones transform from a semiconducting to a quasi‐metallic character. Softening of the q = 0 selection rule is suggested as a possible reason to explain these results. Furthermore, these studies provide a contrasting comparison between MW and SW nanotubes. Copyright © 2006 John Wiley & Sons, Ltd.