In broadband coherent anti-Stokes Raman scattering (CARS) spectroscopy with supercontinuum (SC), the simultaneously detectable spectral coverage is limited by the spectral continuity and the simultaneity of variou...In broadband coherent anti-Stokes Raman scattering (CARS) spectroscopy with supercontinuum (SC), the simultaneously detectable spectral coverage is limited by the spectral continuity and the simultaneity of various spectral components of SC in an enough bandwidth. By numerical simulations, the optimal experimental conditions for improving the SC are obtained. The broadband time-resolved CARS spectrography based on the SC with required temporal and spectral distributions is realised. The global molecular vibrational spectrum with well suppressed nonresonant background noise can be obtained in a single measurement. At the same time, the measurements of dephasing times of various molecular vibrational modes can be conveniently achieved from intensities of a sequence of time-resolved CARS signals. It will be more helpful to provide a complete picture of molecular vibrations, and to exhibit a potential to understand not only both the solvent dynamics and the solute-solvent interactions, but also the mechanisms of chemical reactions in the fields of biology, chemistry and material science.展开更多
We performed femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) measurements on liquid toluene and PVK film. For both samples, we selectively excited the CH stretching vibrational modes and ob...We performed femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) measurements on liquid toluene and PVK film. For both samples, we selectively excited the CH stretching vibrational modes and observed the expected quantum beat signals. The frequency of the well-defined beats is in good agreement with the energy difference between the two simultaneously excited modes, which demonstrates that a coherent coupling between the vibrational modes of the C H chemical bonds exists at the different positions of the molecules. The dephasing times of the excited modes are obtained simultaneously.展开更多
We report on the theoretical and the experimental investigations of the coherent phonon dynamics in sapphire crystal using the femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) technique. The...We report on the theoretical and the experimental investigations of the coherent phonon dynamics in sapphire crystal using the femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) technique. The temporal chirped white-light continuum (WLC) is used for the Stokes pulse, therefore we can perform the selective excitation of the phonon modes without using a complicated laser system. The expected quantum beat phenomenon is clearly observed. The theoretical formulas consist very well with the experimental results. The dephasing times of the excited phonon modes, the wavenumber difference, and the phase shift between the simultaneously excited modes are obtained and discussed. This work opens up a way to study directly high-frequency coherent phonon dynamics in bulk crystals on a femtosecond time scale and is especially helpful for understanding the nature of coherent phonons.展开更多
Raman scattering is a versatile and powerful technique and has been widely used in modern scientific research and vast industrial applications. It is one of the fundamental experimental techniques in condensed matter ...Raman scattering is a versatile and powerful technique and has been widely used in modern scientific research and vast industrial applications. It is one of the fundamental experimental techniques in condensed matter physics, since it can sensitively probe the basic elementary excitations in solids like electron, phonon, magnon, etc. The application of extreme conditions (low temperature, high magnetic field, high pressure, etc.) to Raman scattering, will push its capability up to an unprecedented level, because this enables us to look into new quantum phases driven by extreme conditions, trace the evolution of the excitations and their coupling, and hence uncover the underlying physics. This review contains two topics. In the first part, we will introduce the Raman facility under extreme conditions, belonging to the optical spectroscopy station of Synergetic Extreme Condition User Facilities (SECUF), with emphasis on the system design and the capability the facility can provide. Then in the second part we will focus on the applications of Raman scattering under extreme conditions to a variety of condensed matter systems such as superconductors, correlated electron systems, charge density waves (CDW) materials, etc. Finally, as a rapidly developing technique, time-resolved Raman scattering will be highlighted here.展开更多
Interferometric Rayleigh scattering diagnostic technique for the time-resolved measurement of flow velocity is studied. Theoretically, this systematic velocity-measured accuracy can reach up to 1.23 m/s. Measurement a...Interferometric Rayleigh scattering diagnostic technique for the time-resolved measurement of flow velocity is studied. Theoretically, this systematic velocity-measured accuracy can reach up to 1.23 m/s. Measurement accuracy is then evaluated by comparing with hot wire anemometry results. Moreover, the distributions of velocity and turbulence intensity in a supersonic free jet from a Laval nozzle with a Mach number of 1.8 are also obtained quantitatively. The sampling rate in this measurement is determined to be approximately 10 k Hz.展开更多
The generalized two-dimensional correlation analysis based on time-resolved light scattering patterns (2D TRLS) has been employed to study the phase separation process of an epoxy-amine-polyethersulfone blend in whi...The generalized two-dimensional correlation analysis based on time-resolved light scattering patterns (2D TRLS) has been employed to study the phase separation process of an epoxy-amine-polyethersulfone blend in which the secondary phase separation takes place. The results of the 2D TRLS provided more detailed information that was not readily observed in the 1D TRLS patterns. (i) During the first process of phase separation, the sequential order of coarsening in size of the domains among the larger and smaller ones has been reversed between the diffusion regime and the hydrodynamic regime. (ii) The change of the larger domains in size, due to the hydrodynamic flow in the late stage of the first phase separation process, keeps on taking place earlier than that of the new domains appeared in the secondary phase separation process. (iii) During the secondary phase separation process the size growth of the smaller domains takes place earlier than that of the larger ones, probably due to the assumption that the coarsening mode could decrease the interface tension more quickly.展开更多
Time-resolved X-ray scattering was employed to in-situ monitor the epitaxial growth process of the thin films and multilayers of EuTiO3 and SrTiO3 during pulsed laser deposition. The temporal intensity oscillations of...Time-resolved X-ray scattering was employed to in-situ monitor the epitaxial growth process of the thin films and multilayers of EuTiO3 and SrTiO3 during pulsed laser deposition. The temporal intensity oscillations of the reflected X-rays at auti-Bragg position and the transient processes following the flux pulses were observed. The temporal intensity oscillations were used to control the film thickness, and the reflectivity along the crystal truncation rod was used to measure both the film thickness and the surface/interface roughness. The primary features of the X-ray intensity oscillations were reproduced via simulating the experimental data using diffusive rate equation model. Several mechanisms of determining the X-ray intensity features were discerned.展开更多
A series of fluorocarbon chain terminated polyetherimide is added to epoxy resin, and the effect of molecular weight on the process of phase separation is studied by time-resolved light scattering (TRLS), differential...A series of fluorocarbon chain terminated polyetherimide is added to epoxy resin, and the effect of molecular weight on the process of phase separation is studied by time-resolved light scattering (TRLS), differential scanning calorimeter (DSC), scanning microscopy (SEM). The results indicate that the phase separation rate decreases due to the preventing effect in-duced by low surface energy of fluorocarbon chain terminated polyetherimide. In addition, evolu-tion time of morphology is shortened and the domain size decreases with the introduction of fluorocarbon chain terminated polyetherimide. Furthermore, when the molecular weight of fluorocarbon chain terminated polyetherimide increases, the morphology can change from dis-persed phase to co-continuous phase. Thus, changing the molecular weight of fluorocarbon chain terminated polyetherimide can control the morphology of the epoxy/polyetherimide blend, which is of great significance in many industries.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.60627003)the Foundation for Creative Team in Institution of Higher Education of Guangdong Province,China(Grant No.06CXTD009)
文摘In broadband coherent anti-Stokes Raman scattering (CARS) spectroscopy with supercontinuum (SC), the simultaneously detectable spectral coverage is limited by the spectral continuity and the simultaneity of various spectral components of SC in an enough bandwidth. By numerical simulations, the optimal experimental conditions for improving the SC are obtained. The broadband time-resolved CARS spectrography based on the SC with required temporal and spectral distributions is realised. The global molecular vibrational spectrum with well suppressed nonresonant background noise can be obtained in a single measurement. At the same time, the measurements of dephasing times of various molecular vibrational modes can be conveniently achieved from intensities of a sequence of time-resolved CARS signals. It will be more helpful to provide a complete picture of molecular vibrations, and to exhibit a potential to understand not only both the solvent dynamics and the solute-solvent interactions, but also the mechanisms of chemical reactions in the fields of biology, chemistry and material science.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 20573028 and 20973050)
文摘We performed femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) measurements on liquid toluene and PVK film. For both samples, we selectively excited the CH stretching vibrational modes and observed the expected quantum beat signals. The frequency of the well-defined beats is in good agreement with the energy difference between the two simultaneously excited modes, which demonstrates that a coherent coupling between the vibrational modes of the C H chemical bonds exists at the different positions of the molecules. The dephasing times of the excited modes are obtained simultaneously.
基金supported by the National Natural Science Foundation of China (Grant No. 20973050)
文摘We report on the theoretical and the experimental investigations of the coherent phonon dynamics in sapphire crystal using the femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) technique. The temporal chirped white-light continuum (WLC) is used for the Stokes pulse, therefore we can perform the selective excitation of the phonon modes without using a complicated laser system. The expected quantum beat phenomenon is clearly observed. The theoretical formulas consist very well with the experimental results. The dephasing times of the excited phonon modes, the wavenumber difference, and the phase shift between the simultaneously excited modes are obtained and discussed. This work opens up a way to study directly high-frequency coherent phonon dynamics in bulk crystals on a femtosecond time scale and is especially helpful for understanding the nature of coherent phonons.
基金Project supported by the Ministry of Science and Technology of China(Grant Nos.2016YFA0300504 and 2017YFA0302904)the National Natural Science Foundation of China(Grant Nos.11474357,11774419,11604383,and 11704401)supported by the Scientific Equipment Development Project of Chinese Academy of Sciences(Grant No.YJKYYQ20170027)
文摘Raman scattering is a versatile and powerful technique and has been widely used in modern scientific research and vast industrial applications. It is one of the fundamental experimental techniques in condensed matter physics, since it can sensitively probe the basic elementary excitations in solids like electron, phonon, magnon, etc. The application of extreme conditions (low temperature, high magnetic field, high pressure, etc.) to Raman scattering, will push its capability up to an unprecedented level, because this enables us to look into new quantum phases driven by extreme conditions, trace the evolution of the excitations and their coupling, and hence uncover the underlying physics. This review contains two topics. In the first part, we will introduce the Raman facility under extreme conditions, belonging to the optical spectroscopy station of Synergetic Extreme Condition User Facilities (SECUF), with emphasis on the system design and the capability the facility can provide. Then in the second part we will focus on the applications of Raman scattering under extreme conditions to a variety of condensed matter systems such as superconductors, correlated electron systems, charge density waves (CDW) materials, etc. Finally, as a rapidly developing technique, time-resolved Raman scattering will be highlighted here.
基金Project supported by the National Natural Science Foundation of China(Grant No.11272337)
文摘Interferometric Rayleigh scattering diagnostic technique for the time-resolved measurement of flow velocity is studied. Theoretically, this systematic velocity-measured accuracy can reach up to 1.23 m/s. Measurement accuracy is then evaluated by comparing with hot wire anemometry results. Moreover, the distributions of velocity and turbulence intensity in a supersonic free jet from a Laval nozzle with a Mach number of 1.8 are also obtained quantitatively. The sampling rate in this measurement is determined to be approximately 10 k Hz.
基金supported by the National Natural Science of Foundation of China(NSFC)(Nos.20674014, 20425415,20274010,50103003,20221402)
文摘The generalized two-dimensional correlation analysis based on time-resolved light scattering patterns (2D TRLS) has been employed to study the phase separation process of an epoxy-amine-polyethersulfone blend in which the secondary phase separation takes place. The results of the 2D TRLS provided more detailed information that was not readily observed in the 1D TRLS patterns. (i) During the first process of phase separation, the sequential order of coarsening in size of the domains among the larger and smaller ones has been reversed between the diffusion regime and the hydrodynamic regime. (ii) The change of the larger domains in size, due to the hydrodynamic flow in the late stage of the first phase separation process, keeps on taking place earlier than that of the new domains appeared in the secondary phase separation process. (iii) During the secondary phase separation process the size growth of the smaller domains takes place earlier than that of the larger ones, probably due to the assumption that the coarsening mode could decrease the interface tension more quickly.
文摘Time-resolved X-ray scattering was employed to in-situ monitor the epitaxial growth process of the thin films and multilayers of EuTiO3 and SrTiO3 during pulsed laser deposition. The temporal intensity oscillations of the reflected X-rays at auti-Bragg position and the transient processes following the flux pulses were observed. The temporal intensity oscillations were used to control the film thickness, and the reflectivity along the crystal truncation rod was used to measure both the film thickness and the surface/interface roughness. The primary features of the X-ray intensity oscillations were reproduced via simulating the experimental data using diffusive rate equation model. Several mechanisms of determining the X-ray intensity features were discerned.
文摘A series of fluorocarbon chain terminated polyetherimide is added to epoxy resin, and the effect of molecular weight on the process of phase separation is studied by time-resolved light scattering (TRLS), differential scanning calorimeter (DSC), scanning microscopy (SEM). The results indicate that the phase separation rate decreases due to the preventing effect in-duced by low surface energy of fluorocarbon chain terminated polyetherimide. In addition, evolu-tion time of morphology is shortened and the domain size decreases with the introduction of fluorocarbon chain terminated polyetherimide. Furthermore, when the molecular weight of fluorocarbon chain terminated polyetherimide increases, the morphology can change from dis-persed phase to co-continuous phase. Thus, changing the molecular weight of fluorocarbon chain terminated polyetherimide can control the morphology of the epoxy/polyetherimide blend, which is of great significance in many industries.