三原子分子的喇曼散射

利用U(5)群链描述三原子分子振转谱的对称性质,并用群论方法计算了CO_2分子喇曼散射的跃迁矩阵元,给出了它的振动与转动喇曼散射截面.结果与实验较好地符合.     

Enhanced Raman scattering by molecules adsorbed on electrodes--a theoretical model

The unusually large Raman signals originating from molecules adsorbed on electrode surfaces are postulated to arise from resonance enhancement by electronic processes at the rough metal-eletrolyte surface. By modelling this transition region between metal and eletrolyte with a collection of metallic spheres surrounded by adsorbate and ambient medium on top of a flat metal substrate, satisfactory agreement is obtained between measured and calculated spectra of both ΔR/R and the excitation function of the Raman signals.     

Excitation profiles of resonant coherent Raman scattering by impurity molecules

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.     

Raman scattering activities for partially oriented molecules

Raman scattering activities have been derived for two cases of uniaxially oriented molecules. In the first case, one principal axis of the molecule is held in fixed orientation while the other two axes are randomly oriented. In the second case, one principal axis is confined to a plane while, as before, the other two axes are randomly oriented. Expressions for scattering activities in terms of elements of the derived polarizability tensor are tabulated for three orthogonal sample orientations and for both right-angle and back viewing. These expressions should be useful in interpreting Raman spectra of samples such as stretched polymers, partially ordered polycrystallites, molecules or macro-molecules partially ordered by shear flow, or molecules contained in liquid crystals or clathrates.     

Coherent anti-Stokes resonance Raman scattering of excited molecules

A theoretical investigation of the coherent anti-Stokes resonance Raman scattering (CARRS) of excited molecules is given. The calculation of the anti-Stokes intensity predicts the simultaneous appearance of the vibrational frequencies of the ground and the excited electronic state in the CARRS spectra. The line shape of these spectra and the optimum conditions for the anti-Stokes amplification are discussed.     

Rayleigh and Raman scattering from optically active molecules

The intensity of Rayleigh and Raman scattering from optically active molecules is shown to be slightly different in right and left circularly polarized incident light. The circular intensity differential of the Rayleigh line is dependent on components of the optical activity tensor, and that of the Raman lines is a function of the variation of the optical activity with the vibrational coordinates. This circular intensity differential might be of the order of 10^-3 times that of the Rayleigh or Raman intensity.     

Theory of the rotational structure of resonant Raman scattering by diatomic molecules

The apparatus of irreducible tensor operators is used to calculate the rotational structure of resonant Raman light scattering by freely rotating diatomic molecules. It is shown that solution of the problem reduces to the calculation of certain special coefficients. Their relation to the Placzek-Teller factors (which are well known in the theory of polarizability) is established. The nonzero coefficients are computed for the case when resonant rotational scattering is due to the¹ terms of the diatomic molecule.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 54–58, October, 1987.The author thanks T. N. Popov for interest in the work.     

Raman scattering study of molecules adsorbed on ZnS nanocrystals

The adsorption of 4‐mercaptopyridine (4‐Mpy) molecules on ZnS nanocrystals was investigated by means of Raman spectroscopy. We compared the Raman signals of 4‐Mpy molecules adsorbed on ZnS nanocrystals and Ag substrate. The differences in the adsorption of 4‐Mpy molecules on the semiconductor and the metal substrate were noted. The results demonstrated that adsorbed species on the semiconductor ZnS nanocrystals can be detected by Raman spectroscopy. Copyright © 2006 John Wiley & Sons, Ltd.     

Raman scattering by silicon

Reflection Raman spectroscopy has been performed on silicon at room temperature. One-phonon fine structure, which has been predicted by Cowley and observed in part by Wright et al., is fully obtained. Two-phonon structure is also obtained, which includes the most intense broad band observed by Parker et al. and weak broad bands not observed by them. One- and two-phonon structures reported here are very similar in shape to the ones predicted by Cowley by considering the anharmonicity of the lattice forces.     

Slow-neutron scattering by molecules

We have explicitly calculated the experimental scattering cross-section for homonuclear diatomic molecular perfect gases using virtually exact expressions for the scattering law. These recoil and detector corrections are illustrated for a series of molecules at various temperatures on various instruments. We have shown that the conventional Placzek corrections are quite inadequate for vibrating molecules and we propose a simple recipe which leads to readily calculable expressions which give good agreement with the ‘exact’ results even for nuclei as light as deuterium. This recipe can be generalized for use for almost any nucleus in any molecule and may be expected to materially improve the accuracy of structure determination in molecular gases and liquids. In particular it is found that the Debye-Waller coefficient is very dependent on the experimental parameters. The generalization to time-of-flight experiments is given in the following paper.     

Nonadiabatic effects in diatomic molecules on resonant continuum Raman scattering

Journal of Applied Spectroscopy -     

A comparison of Raman scattering,resonance Raman scattering,and fluorescence from molecules adsorbed on silver island films

The enhancement of Raman scattering (RS), resonance Raman scattering (RRS), and fluorescence from molecules adsorbed on silver-island films is reported. A heirarchy of enhancements is found: 10⁵ for RS, 10³ for RRS, and 0.1–10 for fluorescence, depending on the quantum yield of the free molecule. Using the framework of the electromagnetic theory of surface-enhanced Raman scattering, generalized to treat molecular resonance phenomena, we develop a unified picture of the role of the surface plasmon resonances, and the surface-induced damping, in the light scattering processes. The observed heirarchy of enhancements is shown to have important spectroscopic consequences.     

表面极化声子的喇曼散射研究

本文主要研究表面极化声子的喇曼散射.在探测表面极化声子的衰减全反射方法以及喇曼散射方法的基础上,借鉴了Kretchmann配置的衰减全反射喇曼散射法,提出了Otto配置的衰减全反射喇曼散射法,并以CaF_2单晶体为样品做了一系列实验.同时,本文利用了能量守恒及平行于样品表面的能量守恒关系,利用了格林函数或响应函数所推出的表面极化声子的一般频散关系,理论上给出了CaF_2-空气表面极化声子的一个唯象的频散关系.实验上用特定设计制做的一个样品架对CaF_2样品测定了它与空气界面上的表面极化声子的频散关系,比较结果,理论与实验取得了比较令人满意的一致.     

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.     

Rotational and vibrational states of excitonic molecules in CuBr studied by the two-photon-resonant Raman scattering

Excited states of excitonic molecules are found in the study of the two-photon-resonant Raman scattering. These states consist of four levels and have binding energies of 1.0–1.8 meV, which are very small compared with those of the ground states. They are considered to be the rotational and vibrational states of excitonic molecules.     

Electron scattering by polar molecules

Theoretical and experimental studies of electron-polar molecule collisions are reviewed. Principal emphasis is placed on elastic scattering and excitation of rotational states by low-energy (less than about 10 eV) electrons. After a survey of experimental techniques and methods of cross-section calculation, the results are compared with each other. In particular, the dipole-moment dependence of the cross-section is discussed in relation to possible bound states in a dipole field. Examples of applications of the resulting cross-section are demonstrated. Finally future problems are summarized.     

液相硝基甲烷分子振动特性的相干反斯托克斯拉曼散射光谱

构建时间分辨相干反斯托克斯拉曼散射（CARS）光谱系统,从微观层次研究硝基甲烷的分子相干振动动力学特性.实验中采用超连续白光作为斯托克斯光,通过调整斯托克斯光的时间延迟,得到不同振动模式的CARS光谱.通过对振动弛豫曲线的拟合,获得硝基甲烷分子不同振动模式的振动失相时间.结果表明C–H键伸缩振动比C–N键伸缩振动更容易受热声子的影响.在热加载下,硝基甲烷分子的C–H键有望首先被激发并引起初始化学反应.     

Surface enhanced Raman scattering of molecules related to highly ordered gold cavities

We presented a controlled particles‐in‐cavity (PIC) pattern for surface‐enhanced Raman scattering (SERS) detection. The periodic gold cavity array was fabricated by electrodeposition using highly ordered polystyrene spheres as a template. The as‐prepared gold cavities can be used as a SERS active substrate with significant spectral enhancement and reproducibility, which was evaluated by SERS signals using 4‐mercaptobenzoic acid (4‐MBA) as probe molecules. The surface of these gold cavities was further functionalized with cetyltrimethylammonium bromide molecules, which may immobilize the 4‐MBA‐modified silver nanoparticles in the gold cavity to form a PIC structure via the electrostatic interaction. We have demonstrated that there exists a pH window for the immobilization of the nanoparticles inside cavities. Therefore, the silver nanoparticles can be selectively immobilized into the functionalized gold cavities under the optimized pH value of the media. Further enhancement of the Raman scattering of the labeled molecules can be achieved due to the interconnection between the silver nanoparticles and gold cavity. Copyright © 2013 John Wiley & Sons, Ltd.