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1.
Gadolinium manganese sulfide solid solutions are investigated by infrared and Raman spectroscopy. Longitudinal optical–transverse optical splitting of the manganese–sulfur bond vibration is observed in the vibrational spectra. The Raman spectra contain modes that are prohibited in the crystal structure of the alpha phase of manganese sulfide, which are associated with activation of the phonons from both the Brillouin zone center and its X and L points. The concentration dependence of transverse optical and longitudinal optical modes’ frequencies is calculated within the frame of the modified random-element-isodisplacement model, being in good agreement with the experimental results. Both theory and experiment show that the solid solution under study exhibits a “one-mode” behavior. 相似文献
2.
V. S. Bagaev L. K. Vodop’yanov V. S. Vinogradov V. V. Zaitsev S. P. Kozyrev N. N. Mel’nik E. E. Onishchenko G. Karczewski 《Physics of the Solid State》2004,46(1):173-175
Electronic and vibrational states in CdTe/ZnTe quantum dot superlattices are studied using optical spectroscopy techniques (photoluminescence in a wide temperature range, IR reflection, and Raman scattering). The effect of the ZnTe barrier layer thickness on the luminescence spectra of the structures is discussed. The luminescence from electronically coupled islands is assumed to be due to spatially indirect excitons because of the specific features of the CdTe/ZnTe heterostructure band structure. A combination of quantum-dot vibrational modes, which has not been observed earlier, is detected in the Raman spectra. Analysis of the lattice IR reflection spectra shows that, in the case of large barrier thicknesses between the quantum-dot planes, elastic stresses are concentrated in the Zn1?xCdxTe layers, whereas in structures with lower barrier thicknesses the elastic-strain distribution exhibits a more complicated pattern. 相似文献
3.
V. S. Vinogradov L. K. Vodop’yanov G. Karczewski N. N. Mel’nik 《Physics of the Solid State》2006,48(5):957-961
The Raman spectra of superlattices consisting of layers of CdTe self-assembled quantum dots separated by ZnTe narrow barriers with thicknesses of 10 and 5 monolayers are investigated. It is found that, apart from the bands previously observed at frequencies of ~120 and ~140 cm?1 for samples with thicker barriers (25 and 12 monolayers), the Raman spectra exhibit a band at ~147 cm?1 in the frequency range of CdTe vibrational modes. This band is attributed to a symmetric vibrational mode of a pair of quantum dots with oppositely directed oscillations of the dipole moments. It is this type of vibrational mode in the material surrounding the ZnTe quantum dot that accounts for the shift of the band at ~200 cm?1 near the LO mode of ZnTe vibrations toward lower frequencies. 相似文献
4.
本文介绍GaAs/AlAs超晶格的室温近共振喇曼散射测量结果。由于超晶格中Fr?hlich相互作用的共振增强效应,GaAs LO声子偶模的散射得到了很大的增强。和前人的结果一样,在偏振谱我们观察到了偶模。但和前人的结果不同,在退偏振谱中我们观察到的是奇模,而不是偶模。从而证明了在近共振条件下LO声子限制模仍遵从与非共振时一样的选择定则。二级喇曼散射实验结果表明,在偏振谱中二级谱是由两个偶模组合而成,而在退偏振谱中的二级谱与前人的结果不同,由一个奇模与一个偶模组合而成。上述结果与最近提出的黄朱模型的预言是一
关键词: 相似文献
5.
A. Milekhin Yu. Pusep Yu. Yanovskii V. Preobrazhenskii B. Semyagin 《Physics of the Solid State》1998,40(3):507-509
A study is reported of optical vibrational modes in [311]-grown GaAs/AlAs superlattices. An analysis of the TO and LO localized modes observed in IR reflectance spectra showed that the difference between the TO and LO mode frequencies in superlattices grown on (311)A and (311)B surfaces is due to the different localization lengths of these modes. The dispersion of transverse optical phonons in GaAs
derived from IR reflectance spectra is in a good agreement with Raman scattering data.
Fiz. Tverd. Tela (St. Petersburg) 40, 550–552 (March 1998) 相似文献
6.
The vibrational properties and Raman spectra of graphene nanoribbons with six different edges have been studied by using the first-principles calculations. It is found that edge reconstruction leads to the emergence of localized vibrational modes and new topological defect modes, making the different edges identified by polarized Raman spectra. The radial breathing-like modes are found to be independent of the edge structures, while the G-band-related modes are affected by different edge structures. Our results suggest that the polarized Raman spectrum could be a powerful experimental tool for distinguishing the GNRs with different edge structures due to their different vibrational properties. 相似文献
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在双谐振子近似下,利用耦合微扰Hartree-Fock方法计算了4-N-甲基苯乙烯砒啶盐衍生物分子的静态振动第一超极化率和红外与拉曼光谱,给出了对静态振动第一超极化率起主导贡献的两种简正振动模式. 研究发现,标题分子的静态振动第一超极化率都比较大,且与静态电子第一超极化率呈较好的线性关系. 首次提出了利用红外与拉曼光谱特征峰标识的振动模来估算振动第一超极化率大小的少模方法. 结果表明,少模方法用于估算振动第一超极化率的大小是可行的. 相似文献
9.
Reiner K. Wertheimer 《Molecular physics》2013,111(6):1631-1644
The theory presented in this paper investigates the isotropic Raman spectra of liquid binary mixtures. It is found that the collective vibrational modes of different molecular species can be significantly coupled. This is a consequence of the (nearly) resonant vibrational transfer processes, which give rise to distinct vibrational correlations (i.e. correlations between adjacent molecules). The coupling, however, occurs only with weakly-separated or overlapping bands. The more general results of the theory are applied to isotope mixtures. The spectral information available from relevant dilution experiments is interpreted. In particular it is shown that the spectral properties of the vibrational self-correlation part can be concluded from the observed collective correlation function. The significance of the distinct vibrational correlations with respect to the infrared and depolarized Raman spectra is discussed. 相似文献
10.
The i.r., Raman and depolarization spectra of the amorphous pseudo-binary alloy systems (GeS2)1-χ(As2S3)χ and (GeSe2)1-χ(As2Se3)χ are reported here. In contrast to the one-mode behavior that is anticipated on the basis of the mass ratio of the alloy atoms (Ge/As), two bond-stretching modes are observed in both the i.r. and Raman spectra. This new type of phonon behavior is interpreted in terms of differences in the local coordination via a chemical bonding model. 相似文献
11.
Surface-enhanced Raman spectra of a single Fe-protoporphyrin IX molecule display drastic fluctuations in frequency and intensity. When analyzed in their temporal evolution, the vibrational modes of the molecule undergo an on-off switching behavior that is shown to follow a Lévy statistics. Such a time dependent process may encode both the dynamics of the molecule-environment interactions and the intrinsic gating or activation of the mode emission mechanism. 相似文献
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A. Milekhin T. Werninghaus D.R.T. Zahn Y. Yanovskii V. Preobrazhenskii B. Semyagin A. Gutakovskii 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(3):295-299
The vibrational spectrum of ultra-thin layer GaSb/AlSb superlattices was investigated in detail by infrared (IR) and Raman
spectroscopies. The effect of confinement of the transverse and longitudinal optical phonons in both types of the layers was
studied. The dispersions of optical phonons of the GaSb and the AlSb obtained from the analysis of the Raman and IR spectra
are in a good accordance with the theoretical data and results of neutron scattering experiments. First- and second-order
Raman spectroscopy indicates the presence of intermixture of atoms at the interfaces in the GaSb/AlSb superlattices.
Received: 11 May 1998 / Accepted: 21 July 1998 相似文献
14.
Lattice dynamics of LiNi1−yCoyO2 solid solution are investigated using Raman and FTIR measurements. Evolution of the vibrational spectra, i.e., frequency
shift and band broadening of the stretching modes of either (Ni1−yCoyO2)O6 or LiO6 octahedra, are studied as a function of the calcination temperature of the LiNi1−yCoyO2 solid solution. Results show that the solid solution exhibits a one-mode behavior with an increase of the (Ni1−yCoyO2)n sheet covalency upon substitution of cobalt for nickel. The change in the covalency corresponds to an increase of the Madelung
constant with decreasing the c/a value. The broadening of the vibrational bands for Ni-rich compounds is the result of the
cation mixing in the crystal layers. The partially disordered cation distribution appearing in lithium nickelate materials
can also explain the observed broadening of the Raman spectra.
Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999. 相似文献
15.
《Journal of Molecular Spectroscopy》1987,122(1):196-220
Intensity enhancement effects in vibrational Raman spectra of electronically degenerate states are investigated. It is shown that the fundamental and overtone Raman transitions in Jahn-Teller active modes are strongly intensified via enhancement effects involving the symmetric and anti-symmetric Raman polarizability tensors. Such enhancements ensue via intensity borrowing from the Rayleigh scattering process. It is explicitly shown that the isotropic Raman polarizability tensor associated with these transitions is not subjected to enhancement effects. Thus the intense fundamental and overtone Raman transitions in the Jahn-Teller active modes will be reverse polarized (or depolarized) rather than polarized. Moreover, fundamental and overtone Raman transitions associated with vibrations which couple with Jahn-Teller active modes via mixed cross quadratic nuclear potential interactions may also be intensified and reverse polarized. The present work modifies and extends the selection rules which were established long ago by M. S. Child and H. C. Longuet-Higgins [Philos. Trans. R. Soc. London A 254, 259–294 (1961)]. 相似文献
16.
Raman spectra of LiNbO3: MgO crystals have been obtained and compared with Raman spectra of pure LiNbO3 crystals. For both of the two kinds of Raman active modes (4A1+9E), no changes of the numbers, frequency-shifts, and relative intensities of the Raman spectral lines are found. However, it is observed that some modes coupled to each other at room temperature. The observed modes coupling phenomena, disappeared at low temperature. It is shown from these results that the Raman spectral lines of A1 (TO) and E (TO) vibrational modes are mainly determined by the (NbO6) oxygen octahedra characteristic groups of LiNbO3 crystals. 相似文献
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18.
A. G. Milekhin A. I. Nikiforov O. P. Pchelyakov S. Schulze D. R. T. Zahn 《JETP Letters》2001,73(9):461-464
Ge/Si superlattices containing Ge quantum dots were prepared by molecular beam epitaxy and studied by resonant Raman scattering. It is shown that these structures possess vibrational properties of both two-and zero-dimensional objects. The folded acoustic phonons observed in the low-frequency region of the spectrum (up to 15th order) are typical for planar superlattices. The acoustic phonon lines overlap with a broad emission continuum that is due to the violation of the wave-vector conservation law by the quantum dots. An analysis of the Ge and Ge-Si optical phonons indicates that the Ge quantum dots are pseudoamorphous and that mixing of the Ge and Si atoms is insignificant. The longitudinal optical phonons undergo a low-frequency shift upon increasing laser excitation energy (2.54–2.71 eV) because of the confinement effect in small-sized quantum dots, which dominate resonant Raman scattering. 相似文献
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20.
K. N. Boldyrev B. N. Mavrin M. N. Popova L. N. Bezmaternykh 《Optics and Spectroscopy》2011,111(3):420-425
The polarized Raman and reflection spectra of a single crystal YbAl3(BO3)4 at room temperature were studied. Raman active vibrational modes A
1, E
TO, and E
LO are identified. In the Raman spectrum, we detected an intense line at a frequency of 1018 cm−1, which refers to internal vibrations of the BO3 group and is known to be promising for use in amplifiers based on stimulated Raman scattering. From the simulation of reflection
spectra by the method of dispersion analysis the frequencies of A
2 vibrational modes were determined. Intense bands observed in the low-temperature transmission spectra in the range of f-f transitions in the Yb3+ ion are attributed to electron-phonon transitions. The Raman lines are compared with electron-phonon lines in the transmission
spectrum. 相似文献