Multiphonon resonant Raman scattering in GaSe

Multiphonon resonant Raman scattering up to 4 phonons in GaSe has been measured. The results are interpreted by a simple cascade theory. It is shown that the dispersion of RRS here is dominated by resonances with the exciton states.     

Multiphonon Raman scattering from individual single-walled carbon nanotubes

Combinations of up to 6 zone-edge and zone-center optical phonons are observed in the Raman spectra of individual single-walled carbon nanotubes (SWNTs). These multiphonon Raman modes exhibit distinct signatures of the one-dimensional nature of SWNTs and provide information on the phonon structure, exciton-phonon coupling, and excitonic transitions in nanotubes.     

Multiphonon atom-surface scattering from corrugated surfaces: derivation of the inelastic scattering spectrum for diffraction states

A strictly quantum mechanical derivation of the energy and parallel momentum resolved scattering spectrum formula that combines the effects of the diffraction of atoms from corrugated surfaces and multiple inelastic scattering by dispersive phonons is presented. The final result is expressed in the compact and numerically tractable form of a Fourier transform of a cumulant expansion in which each term embodies an interplay between the processes of projectile diffraction and multiphonon scattering to all orders in the respective interaction potentials. The Debye-Waller reduction of the intensities of diffraction peaks is explicitly formulated.     

半导体超晶格的多声子拉曼散射研究

半导体超晶格的多声子拉曼散射研究／张树霖，杨昌黎，侯勇田（北京大学物理系北京１００８７１）彭中灵，李杰，袁诗鑫（中科院上海技物所上海２０００８３）Ｒ．Ｐｌａｎｅｌ（ＭｉｃｒｏｓｔｒｕｃｔｕｒｅｓａｎｄＭｉｃｒｏｅｌｅｃｔｒｏｎｉｃｓＬａｂｏｒａｔｏｒ...     

Multiphonon atomic scattering by solid surfaces

A multiphonon solution for the problem of atom-surface scattering at thermal energies is proposed. The scattering equations are solved using the assumption of low inelastic scattering intensities, and the theoretical formalism is basically an improvement of a previous work on one-phonon scattering. Present results reduce to the one-phonon expression of the previous work when the appropriate limit is taken.     

The Application of New Technology for Raman Spectroscopy

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RecentAdvancesinBiophysical／Biochemical／BiomedicApplicationsofRamanSpectroscopy

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Spin-flip Raman scattering from electrons in localized donor states in n-InSb

We report the first observation of spin-flip Raman scattering from electrons localized in shallow donor states in InSb. For a non-degenerate n-InSb sample (8×10¹³ cm^-3) measurements of the spin-flip Raman gain and the effective g-value as a function of the magnetic field show lineshapes and magnetic field dependences completely different to that of an InSb sample with the electron gas being in a degenerate regime (1.35×10¹⁵ cm^-3). For the 8×10¹³ cm^-3 InSb sample, at magnetic fields greater than 11.5 kG, a splitting of the spin-flip Raman line into two lines is observed which may be an indication that two shallow donor states with different effective g-values are concerned.     

Structural changes in excited states and photoisomers determined by time-resolved Raman scattering

Molecules in the excited singlet and triplet state and photoproducts occuring after photoisomerization or proton transfer are investigated by time-resolved resonance Raman and resonance CARS spectroscopy with nanosecond time resolution. From the time-resolved spectra information on structures and bond strengths of these short-lived species and on their kinetics are obtained.     

Stimulated multipole Raman scattering between opposite-parity states of atomic potassium

Stimulated multipole Raman scattering by free atoms has been observed for the first time. Tunable Stokes emissions close to the 3d-4p transitions in potassium vapour were readily detected when the incident laser frequency was tuned in the region of the 4s-3d electric quadrupole resonances.     

Raman scattering from two-phonon resonance states in SrTiO3

Two-phonon Raman spectroscopy has been performed on SrTiO₃ from 13.3 to 295 K. In the low frequency region, softenings of two bands are observed. With decreasing temperature, they showed sharpening of structure and intensity transfer. It is concluded that one band comes from two-phonon resonance state of ferroelectric soft mode. Theoretical investigations are performed by using thermodynamic Green's function and by taking into account quartic anharmonicity of the lattice force.     

Multiphonon resonances in the Debye-Waller factor of atom surface scattering

He atom surface scattering by dispersionless phonons is treated employing coupled channel (CC) calculations. At low energies, they predict a behavior opposite to perturbative Born or "exponentiated" Born approximation: strong resonant phonon stimulated elastic and inhibited inelastic scattering. The corresponding resonances have not been observed in earlier CC results since these have considered only the temperature dependence of the Debye-Waller factor at higher energy or omitted the attractive well. The resonances can be interpreted in terms of bound states in the attractive well with several excited vibrational quanta. They may be observable for, e.g., He scattering by a cold Xe/Cu surface.     

Investigation of amorphous states of SiO2 by Raman scattering spectroscopy

The vitreous SiO₂ samples irradiated with fast neutrons at a dose of 5×10¹⁷?2.2×10²⁰ per cm² are investigated by the Raman scattering technique. It is demonstrated that the maximum of the low-frequency Raman spectrum (boson peak) shifts with an increase in the irradiation dose, and the medium-range order size decreases from 25 Å for the initial glass to 19 Å for the sample subjected to irradiation at a maximum dose. It is revealed that the fast relaxation intensity obtained from analysis of the low-frequency Raman spectra linearly correlates with the specific volume of the studied samples.     

Raman gap solitons

We show that an intense pump pulse, detuned far from the Bragg resonance of a nonlinear periodic structure, can excite a gap soliton at a wavelength within the band gap that corresponds to the Raman shift of the medium. This Raman gap soliton is a stable, long-lived, quasistationary excitation that exists within the grating even after the pump pulse has passed. We find both stationary solitons as well as slow Raman gap solitons with velocities as low as 1% of the speed of light. The predicted phenomena should be observable in fiber Bragg gratings and other nonlinear photonic band gap structures.     

Theory of Raman scattering and infrared absorption by interacting phonon-magnon states in FeF2

It is shown theoretically that, in the presence of a strong magnetic field, effects due to the interaction betweenB _1g ,E _g,TA phonons and magnons should be important in the Raman and infrared absorption spectrum of FeF₂. As a result the two magnon line should split. A microscopic Hamiltonian for the interactions has been derived. The calculated values of theE _g phonon-one magnon interaction, 9.9 cm^–1, and of theB _1g phonon-two magnon coupling, 6.3 cm^–1, are comparable to those in FeCl₂2H₂O metamagnet, in which C phonon-magnon hybrydization has been observed [1]. It is shown that hybridization between two magnon andB _1g orTA phonon can occur in FeF₂ if the magnon energy approaches the phonon energy due to increasing magnetic field or increasing temperature.On the leave from Technical University, Pozna, Institute of Physics, Pozna 61–138 Piotrowo 3, Poland     

First-order Raman scattering in germanium resonant with the E0 gap

We have measured the absolute Raman efficiency as well as the dispersion for first order scattering by the optical zone center phonon in germanium with the incident photon energies in the range of the E₀ gap energy. At 77 K a Raman polarizability of 68±14 Ų is found for an incident photon energy of 0.826 eV. The deformation potential d is determined to be 40 eV assuming C^″₀ ? 1 for the strength parameter of the E₀ gap.