Hyper-Raman scattering
The hyper-Raman scattering (HRS) from materials is observed in the spectral range of the doubled
frequency 2 I at an intense irradiation of the I frequency. The HRS intensity is proportional to the square of the
pumped intensity and hence it is a nonlinear process concerned with the cubic nonlinearity of material. According to
the selection rules in HRS may be active vibrations that are forbidden in Raman and IR spectra. The important
feature of HRS is an activity of dipole modes in all media.
One of main achievements of the Laboratory is the development of HRS spectroscopy [1]. Using the HRS
technique we have revealed modes forbidden in Raman and IR spectra, determined optical and molecular parameters
for series of materials. We have found out polaritons [2-4] and LO-TO splitting of dipole modes in glasses and
liquids [5], polariton Fermi-resonances
(Fig. 1) and polariton-vibrational
resonances in centrosymmetrical media.
Fig. 1. Hyper-Raman spectra (left) and
dispersion of E1-polaritons (right) in the
region of two-phonon states of calcite.
[6].
HRS is unique technique to
study bulk polaritons and related effects
in centrosymmetrical media. Using HRS we investigated low-frequency spectra of dipole soft modes in
centrosymmetrical crystals, that are forbidden in Raman scattering and complex for the study in IR. In HRS became
first possible to study the dependence of spectra on the magnitude and the direction of the wavevector of vibrations
in glasses and liquids. With use of HRS was proposed and proved a new interpretation of vibrational spectra of
glasses and liquids based on an average symmetry of media [7].
1.
2.
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5.
6.
7.
V.N.Denisov, B.N.Mavrin, V.B.Podobedov. Hyper-Raman scattering by vibrational excitations in crystals,
glasses and liquids. Phys.Rep., 151, 1 (1987).
V.N.Denisov, B.N.Mavrin, V.B.Podobedov, Kh.E.Sterin. Hyper-Raman scattering by polaritons in
centrosymmetrical crystal of SrTiO3. Pis’ma ZhETF, 31, 111 (1980).
V.N.Denisov, B.N.Mavrin, V.B.Podobedov, Kh.E.Sterin. Hyper-Raman scattering by polaritons in liquid
CCl4. Letters to JETP, v.35, 312 (1982).
V.N.Denisov, B.N.Mavrin, V.B.Podobedov, Kh.E.Sterin. Hyper-Raman scattering by polaritons in fused
quartz. Letters to JETP, v.32, 340 (1980).
V.N.Denisov, B.N.Mavrin, V.B.Podobedov, Kh.E.Sterin. Hyper-Raman scattering and TO-LO splitting of
modes in fused quartz. Fizika Tverdogo Tela, 20, 340 (1978).
V.N.Denisov, B.N.Mavrin, V.B.Podobedov, Kh.E.Sterin. Anharmonicity effects in hyper-Raman polariton
spectra in calcite. Zh.Exp.Teor.Fiz., 82, 406 (1982).
V.N.Denisov, B.N.Mavrin, V.B.Podobedov, Kh.E.Sterin. Hyper-Raman scattering and selection rules for
the wave vectors and matrix element in vibrational spectra of glasses and liquids. JETP, v.84, 1266 (1983).