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1.
The phase recovery from the vibrational Raman excitation profile (REP), which contains only the modulus of the Raman amplitude, is discussed for the general situation where the Raman amplitude, with excitation energy extended in the complex plane, may have zeros in the right-half plane. The focus is on the dispersion method, with all results derived by contour integration. The new results for phase recovery, however, apply to both the dispersion and maximum entropy methods. An iterative procedure, with rapid convergence, is presented to overcome the experimental REP data being given in a limited energy range. The forward transform from the electronic absorption spectrum (ABS) to the REP and the inverse transform from the REP to the ABS are presented in a unified manner. The ubiquitous Hilbert transform is shown to be readily evaluated by the fast Fourier transform algorithm. Calculations are presented for β-carotene, a two-mode harmonic model with diffuse vibrational structure, azulene and iodobenzene to illustrate the theory. © 1997 John Wiley & Sons, Ltd. 相似文献
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G. S. N. Eliel H. B. Ribeiro K. Sato R. Saito Chun-Chieh Lu Po-Wen Chiu C. Fantini A. Righi M. A. Pimenta 《Brazilian Journal of Physics》2017,47(6):589-593
A resonant Raman study of twisted bilayer graphene (TBG) samples with different twisting angles using many different laser lines in the visible range is presented. The samples were fabricated by CVD technique and transferred to Si/SiO2 substrates. The Raman excitation profiles of the huge enhancement of the G-band intensity for a group of different TBG flakes were obtained experimentally, and the analysis of the profiles using a theoretical expression for the Raman intensities allowed us to obtain the energies of the van Hove singularities generated by the Moiré patterns and the lifetimes of the excited state of the Raman process. Our results exhibit a good agreement between experimental and calculated energies for van Hove singularities and show that the lifetime of photoexcited carrier does not depend significantly on the twisting angle in the range intermediate angles (?? between 10° and 15°). We observed that the width of the resonance window (Γ ≈ 250 meV) is much larger than the REP of the Raman modes of carbon nanotubes, which are also enhanced by resonances with van Hove singularities. 相似文献
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We investigate the generation and the evolution of continuous-variable (CV) entanglement from a laser-driven four-state atom inside a doubly resonant cavity under Raman excitation. Two transitions in the four-state atom independently interact with the two cavity modes, while two other transitions are driven by coupling laser fields. By including the atomic relaxation as well as cavity losses, we show that the CV entanglement with large mean number of
photons can be generated in our scheme. We also show that the intensity of the coupling laser fields can influence effectively the entanglement period of the cavity field. Different from the conventional resonant excitation scheme where zero one-photon detuning are required, it is found that the intensity and period of entanglement between the two cavity modes as well as the total mean photon number of the cavity field can be adjusted by properly
modulating the frequency detuning. 相似文献
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The impurity is shown to transit into the state of non-linear electron-phonon oscillation upon the passage of a resonance electromagnetic wave pulse. In this case some lines appear in the Raman spectrum at frequencies characteristic for the oscillations. 相似文献
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The ν1 band profile of isotropic Raman spectrum of pure CD4 and its mixtures with Ar and Kr is recorded in the temperature range 140–360 K at pressure of pure CD4 ranging from 4 to 20 atm and at total pressure of gas mixtures in the interval 4–160 atm. The dependences of the band shape on temperature and density are analyzed. The coefficients of the CD4 band broadening by Ar and Kr are determined, and the decisive role of vibrational contributions, in particular of the intramolecular energy transfer, is pointed out. 相似文献
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A new method of taking Raman and two-photon-excited luminescence spectra in an ultradispersed medium is proposed. In this
method, optical fibers serve to introduce an exciting radiation into and extract the secondary radiation from an ultradispersed
medium placed in a cavity-type metallic cell. The spectra are initiated with a pulsed-periodic light source (copper vapor
laser) and are recorded using a gating system. The contrast of the secondary radiation spectra is high with respect to the
exciting radiation, allowing for molecular analysis of ultradispersed media by means of a single small-size monochromator. 相似文献
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XU Jianqiu LOU Qihong 《Chinese Journal of Lasers》1998,7(4):353-356
1IntroductionBroadbandstimulatedRamanscatering(SRS)hasbeenusedinanumberoffields,includingwavelengthconversion,beamcleanupandp... 相似文献
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N. Soin S. S. Roy S. C. Ray J. A. McLaughlin 《Journal of Raman spectroscopy : JRS》2010,41(10):1227-1233
Vertically aligned multiwalled carbon nanotubes (MWCNTs) were grown on 1‐ and 3‐nm cobalt (Co) films, at various growth times by microwave plasma enhanced chemical vapor deposition technique and their microstructural properties were analyzed with the help of Raman spectra that were obtained from different sources of laser excitation energies (EL: 2.41, 1.96 and 1.58 eV). The variation of D and G band positions in MWCNTs grown on 1‐ and 3‐nm Co films follows a similar behavior, and an anomalous behavior was observed in the EL dependence of the D′‐band wavenumber. In the second‐order spectra, the G′ band varied strongly according to structure with the laser excitation energy (EL). The ID/IG ratio decreased with the increase of EL for all MWCNTs; however, for a fixed EL, the ID/IG dispersion is higher at lower EL. The crystallite sizes were estimated using IDIG and EL. We have shown that, for all MWCNTs, ID/IG ratio is inversely proportional to . Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Imbi Tehver Helle Kaasik Vladimir Hizhnyakov 《Journal of Raman spectroscopy : JRS》2011,42(11):1958-1962
The amplitudes and the excitation profiles of coherent resonant Raman scattering (coherent anti‐Stokes and Stokes Raman scattering (CARS and CSRS)) by impurity centers in crystals and/or molecules in solutions are studied, taking into account the coherence of the excited mode and the inhomogeneity of the environment. The CARS and CSRS excitation profiles can directly be related to one‐photon absorption when using the transform theory known from spontaneous resonant Raman scattering. The enlargement of the amplitude of the active mode reveals itself in an enhancement of the vibrational overtones. At large amplitudes, a splitting in the profiles caused by the contribution of two turning points of a strong coherent vibration is observed. The inhomogeneous broadening is different in the excitation profiles of CARS and CSRS. The overlapping contributions to spectrally narrow and broad transitions lead to Fano peculiarities. The effects are illustrated by model calculations. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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基于统计信号处理技术的贝叶斯(Bayes)估计原理,提出一种新的滤波方法。该方法能有效减少散斑条纹图中的噪声,而且仅用一幅散区斑条纹图就能获得准确的条纹相位分布,通过实例说明了该方法的处理过程。 相似文献
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Experimental Investigation on Selective Excitation of Two-Pulse Coherent Anti-Stokes Raman Scattering 下载免费PDF全文
Selective excitation of coherent anti-Stokes Raman scattering from the benzene solution is achieved by adaptive pulse shaping based on genetic algorithm, and second harmonic generation frequency-resolved optical gating (SHG-FROG) technique is adopted to characterize the original and optimal laser pulses. The mechanism for two-pulse coherent mode-selective excitation of Raman scattering is experimentally investigated by modulating the pump pulse in the frequency domain, and it is indicated that two-pulse coherent mode-selective excitation of Raman scattering mainly depends on the effective frequency components of the pump pulse related to specific vibrational mode. The experimental results suggest that two-pulse CARS has good signal-to-background ratio and high sensitivity, and it has attractive potential applications in the complicated molecular system. 相似文献
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Pyatyshev A. Yu. Skrabatun A. V. Rusak A. A. Sverbil P. P. Voinov Yu. P. 《Journal of Russian Laser Research》2021,42(6):645-649
Journal of Russian Laser Research - We record stimulated Raman scattering spectra in chemically-pure glycerol with the formation of two Stokes satellites with equidistant Raman frequencies ν =... 相似文献
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采用高温固相法合成了一种单一相LiCa3MgV3O12:Eu3+白光发光粉,研究了不同的合成温度和不同Eu3+掺杂浓度等条件对其发光性能的影响。该发光粉在近紫外光激发下呈现由两个谱带组成的发射光谱,分别是峰值为530nm的[VO4]3-的特征宽带和峰值为610nm的Eu3+的特征宽带,通过调整合适的Eu3+掺杂量它们可混合成白光,当Eu3+掺杂摩尔分数为0.01时,发光粉的色品坐标为(x=0.33,y=0.34),显色指数为87。该发光粉可和具有近紫外光发射的InGaN管芯配合制得白光LED,极具应用价值。 相似文献
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V. G. Beshenkov A. G. Znamenskii A. V. Irzhak V. A. Marchenko 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2018,12(5):861-865
The problem concerning the diagnostics of the phase composition of lead-zirconate-titanate (PZT) films under conditions of overlapping Raman spectra is solved via applied mathematical statistics. The proposed phase-identification method based on reference spectra is implemented using different Raman-spectrum regions measured on the surface of multiphase PZT films. It is demonstrated that the identification of phases, as well as determination of their concentration, must be performed using the spectral range in which the calculated first principal components of the set of Raman spectra differ to the greatest extent from each other. 相似文献
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DING Liang’en 《中国光学快报(英文版)》2002,11(1)
In this paper, an experiment in a sodium vapor cell with cw laser pumping is reported. Two dips in the excitation spectrum profile of the sodium \$D1\$ line are observed. Theoretically excitation spectra in the three-level system are calculated in detail and results are identical with experiments. It is demonstrated that the appearance of the two dips in the excitation spectrum is close connected with quantum interference effect. 相似文献