Raman spectra of LiNbO_(3) crystals with different hydrogen-ion-exchanged time were examined.E(TO)and A1(TO)modes appear gradually in the transverse A1-and E-symmetry spectra respectively with increasing the exchange ...Raman spectra of LiNbO_(3) crystals with different hydrogen-ion-exchanged time were examined.E(TO)and A1(TO)modes appear gradually in the transverse A1-and E-symmetry spectra respectively with increasing the exchange time and the dependence of their intensities on the exchange time is also observed.We attribute these results to both the internal strains resulting from the ordering-disordering distribution of H ions in the sample and the enhanced photorefractive effect.展开更多
Temperature dependence of Raman spectra of ferroelectric liquid crystal MBOPDOB is examined in spectral region 0-30cm-1 with spectral emphasis on the quasielastic light scattering near solid-Sm C*transition.The quasie...Temperature dependence of Raman spectra of ferroelectric liquid crystal MBOPDOB is examined in spectral region 0-30cm-1 with spectral emphasis on the quasielastic light scattering near solid-Sm C*transition.The quasielastic components are well fitted to Debye-type susceptibility function.With increase of temperature the inverse of the relaxation time T linearly goes to zero in the temperature range below the transition,manifesting a critical slowing-down.The relaxation time keeps same big value in the Sm C*phase as that at the transition point owing to long orientational relaxation in the liquid phase.展开更多
Phase transitions of the ferroelectric liquid crystal were studied by recording low-frequency Raman spectra and three Raman lines at 15,49 and 93cm^(-1) were observed.The intensities of the 15 and 49 cm^(-1) modes red...Phase transitions of the ferroelectric liquid crystal were studied by recording low-frequency Raman spectra and three Raman lines at 15,49 and 93cm^(-1) were observed.The intensities of the 15 and 49 cm^(-1) modes reduce to zero at smectic C*transition temperature,and in the isotropic phase the 93cm^(-1) Raman line with partial frequency shift totally disappears.展开更多
Concentration-dependent Raman spectra of Y_(1-x)Gd_(x)Ba_(2)Cu_(3)O_(7-δ)(x=0.4,0.6,0.8 and 1.0)show that the Raman mode from O(4)bridging shifts upward due to the increased symmetry of crystal potential.The linewidt...Concentration-dependent Raman spectra of Y_(1-x)Gd_(x)Ba_(2)Cu_(3)O_(7-δ)(x=0.4,0.6,0.8 and 1.0)show that the Raman mode from O(4)bridging shifts upward due to the increased symmetry of crystal potential.The linewidth and intensity of 508cm^(-1)mode are decreased and increased with increasing x,respectively which is attributed to the charge transfer from the CuO basal planes to the CuO_(2)planes.Two second-order Raman modes at 798 and 896cm^(-1)have been observed and confirmed.展开更多
文摘Raman spectra of LiNbO_(3) crystals with different hydrogen-ion-exchanged time were examined.E(TO)and A1(TO)modes appear gradually in the transverse A1-and E-symmetry spectra respectively with increasing the exchange time and the dependence of their intensities on the exchange time is also observed.We attribute these results to both the internal strains resulting from the ordering-disordering distribution of H ions in the sample and the enhanced photorefractive effect.
基金Supported by the National Natural Science Foundation of China.
文摘Temperature dependence of Raman spectra of ferroelectric liquid crystal MBOPDOB is examined in spectral region 0-30cm-1 with spectral emphasis on the quasielastic light scattering near solid-Sm C*transition.The quasielastic components are well fitted to Debye-type susceptibility function.With increase of temperature the inverse of the relaxation time T linearly goes to zero in the temperature range below the transition,manifesting a critical slowing-down.The relaxation time keeps same big value in the Sm C*phase as that at the transition point owing to long orientational relaxation in the liquid phase.
基金Supported by the National Natural Science Foundation of China.
文摘Phase transitions of the ferroelectric liquid crystal were studied by recording low-frequency Raman spectra and three Raman lines at 15,49 and 93cm^(-1) were observed.The intensities of the 15 and 49 cm^(-1) modes reduce to zero at smectic C*transition temperature,and in the isotropic phase the 93cm^(-1) Raman line with partial frequency shift totally disappears.
基金the National Center for Research and Development on.Superconductivity of China.
文摘Concentration-dependent Raman spectra of Y_(1-x)Gd_(x)Ba_(2)Cu_(3)O_(7-δ)(x=0.4,0.6,0.8 and 1.0)show that the Raman mode from O(4)bridging shifts upward due to the increased symmetry of crystal potential.The linewidth and intensity of 508cm^(-1)mode are decreased and increased with increasing x,respectively which is attributed to the charge transfer from the CuO basal planes to the CuO_(2)planes.Two second-order Raman modes at 798 and 896cm^(-1)have been observed and confirmed.
