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ultrafast dynamics in photo-excited Mott insulator Sr_(3)Ir_(2)O_7 at high pressure

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Chinese Physics B 2024年第1期33卷 149-155页

作者：尹霞张建波王东 Takeshi Nakagawa 夏春生张曹顺郭伟程昌峻丁阳 Center for High-Pressure Science and Technology Advanced Research Beijing 100094China College of Physics and Information Technology Shaanxi Normal UniversityXi'an 710119China

High-pressure ultrafast dynamics,as a new crossed research direction,are sensitive to subtle non-equilibrium state changes that might be unresolved by equilibrium states measurements,providing crucial information for studying delicate phase transitions caused by complex interactions in Mott *** time-resolved transient reflectivity measurements,we identified the new phases in the spin–orbit Mott insulator Sr_(3)Ir_(2)O_7 at 300 K that was previously unidentified using conventional approaches such as x-ray *** pressure-dependent variation of the amplitude and lifetime obtained by fitting the reflectivity?R/R reveal the changes of electronic structure caused by lattice distortions,and reflect the critical phenomena of phase *** findings demonstrate the importance of ultrafast nonequilibrium dynamics under extreme conditions for understanding the phase transition of Mott insulators.

关键词： ultrafast dynamics high pressure phase transition Mott insulator

Investigation of ultrafast dynamics of CdTe quantum dots by femtosecond fluorescence up-conversion spectroscopy

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Chinese Physics B 2012年第10期21卷 466-471页

作者：姚关心吕良宏桂美芳张先燚郑贤锋季学韩张宏崔执凤 Anhui Institute of Optics and Fine Mechanics Chinese Academy of Sciences Institute of Atomic and Molecular Physics Anhui Normal University College of Chemistry and Materials Science Anhui Normal University Van't Hoff Institute for Molecular Sciences University of AmsterdamScience Park 9041090 GD AmsterdamThe Netherlands

The ultrafast carrier relaxation processes in CdTe quantum dots are investigated by femtosecond fluorescence upconversion ***-excited hole relaxing to the edge of the forbidden gap takes a maximal time of ～ 1.6 ps with exciting at 400 nm,depending on the state of the photo-excited *** shallow trapped states and deep trap states in the forbidden gap are confirmed for CdTe quantum *** addition,Auger relaxation of trapped carriers is observed to occur with a time constant of ～ 5 ps.A schematic model of photodynamics is established based on the results of the spectroscopy *** work demonstrates that femtosecond fluorescence up-conversion spectroscopy is a suitable and effective tool in studying the transportation and conversion dynamics of photon energy in a nanosystem.

关键词： CdTe quantum dots femtosecond fluorescence up-conversion spectroscopy ultrafast dynamics nanomaterial

Probing the ultrafast dynamics in nanomaterial complex systems by femtosecond transient absorption spectroscopy

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High Power Laser Science and Engineering 2016年第3期4卷 13-22页

作者： Qun Zhang Yi Luo Hefei National Laboratory for Physical Sciences at the Microscale Department of Chemical Physics and Synergetic Innovation Center of Quantum Information & Quantum Physics University of Science and Technology of China

Over the past decade the integration of ultrafast spectroscopy with nanoscience has greatly propelled the development of nanoscience, as the key information gleaned from the mechanistic studies with the assistance of ultrafast spectroscopy enables a deeper understanding of the structure–function interplay and various interactions involved in the *** mini-review presents an overview of the recent advances achieved in our ultrafast spectroscopy laboratory that address the ultrafast dynamics and related mechanisms in several representative nanomaterial complex systems by means of femtosecond time-resolved transient absorption spectroscopy. We attempt to convey instructive, consistent information regarding the important processes, pathways, dynamics, and interactions involved in the nanomaterial complex systems,most of which exhibit excellent performance in photocatalysis.

关键词： nanomaterials time-resolved femtosecond pump-probe transient absorption spectroscopy ultrafast dynamics

Cation and anion substitution effects on the ultrafast dynamics of interionic interaction in imidazolium based ionic liquids

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Science China Chemistry 2011年第9期54卷 1491-1497页

作者： LU Rong WANG Wei YU AnChi Department of Chemistry Renmin University of China Beijing 100872 China

Room-temperature Ionic Liquids(ILs) have numerous unique properties that differ from those of conventional molecular *** the unique properties of ILs have been suggested to origin from their microscopic interionic interaction,detailed dynamics of interionic interaction of ILs has not been fully ***,with the Femtosecond Optical Heterodyne-Detected Raman Induced Kerr Effect Spectroscopy(fs-OHD-RIKES),we measured the ultrafast dynamics of the interionic interaction of three typical imidazolium based ILs,1-butyl-3-methylimidazolium tetrafluoroborate([bmim][BF4]),1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]),and 1-decyl-3-methylimidazolium tetrafluoroborate([dmim][BF4]).We observed several periods of subpicosecond oscillation in their fs-OHD-RIKES *** decomposing their fs-OHD-RIKES signals into four Brownian oscillators in time domain,we explored the cation and anion substitution effects on the ultrafast dynamics of interionic interaction of *** found that the cation substitution affected all the low frequency motions we observed,while the anion substitution only affected the two higher low frequency motions.

关键词： Brownian oscillator ultrafast dynamics interionic interaction ionic liquid Raman induced Kerr effect spectroscopy

ultrafast dynamics observation during femtosecond laser-material interaction

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International Journal of Extreme Manufacturing 2019年第3期1卷 62-84页

作者： Baoshan Guo Jingya Sun YongFeng Lu Lan Jiang Laser Micro/Nano Fabrication Laboratory School of Mechanical EngineeringBeijing Institute of TechnologyBeijing100081People’s Republic of China Department of Electrical and Computer Engineering University of Nebraska-LincolnLincolnNE 68588-0511United States of America

Femtosecond laser technology has attracted significant attention from the viewpoints of fundamental and application;especially femtosecond laser processing materials present the unique mechanism of laser-material *** the extreme nonequilibrium conditions imposed by femtosecond laser irradiation,many fundamental questions concerning the physical origin of the material removal process remain *** this review,cutting-edge ultrafast dynamic observation techniques for investigating the fundamental questions,including timeresolved pump-probe shadowgraphy,ultrafast continuous optical imaging,and four-dimensional ultrafast scanning electron microscopy,are comprehensively *** technique is described in depth,beginning with its basic principle,followed by a description of its representative applications in laser-material interaction and its strengths and *** consideration of temporal and spatial resolutions and panoramic measurement at different scales are two major ***,the prospects for technical advancement in this field are discussed finally.

关键词： ultrafast dynamics pump-probe shadowgraphy ultrafast continuous optical imaging 4D ultrafast scanning electron microscopy femtosecond laser manufacturing

ultrafast dynamics of trans-4-diethylaminoazobenzene studied by femtosecond transient absorption spectroscopy

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Ultrafast dynamics of trans-4-diethylaminoazobenzene studied...

ultrafast carrier dynamics in GeSn thin film based on time-resolved terahertz spectroscopy

中国化学会第29届学术年会

作者： Ya-ping Wang Song Zhang Si-mei Sun Kai Liu Bing Zhang State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and Mathematics Chinese Academy of Sciences

The ultrafast excited state dynamics of trans-4-diethylaminoazobenzene with the S2 state excitation was investigated in several solvents by femtosecond transient absorption spectroscopy. Following excitation to the S2 state, the internal conversion to the S1 state was observed within 70 fs. The decay of the S1 state includes isomerization to the hot S0 state of cis isomer and internal conversion to the hot S0 state of trans isomer. Solvent effect was observed in the decay of the S1 state of trans isomer and the vibration relaxation of the hot S0 state of cis isomer. The lack of solvent viscosity dependence of the S1-state lifetime indicates that the photoisomerization is not by rotation mechanism but by inversion mechanism. The S1-state lifetime is slower with the increase of solvent polarity, since the energy gap between the S0 and S1 state is larger. The vibrational cooling of the hot S0 state of cis isomer is faster in protic solvents since the H-bond was formed.

关键词： trans-4-diethylaminoazobenzene photoisomerization transient absorption spectroscopy solvent effect ultrafast dynamics

来源： cnki会议评论

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Chinese Physics B 2024年第1期33卷 164-169页

作者：黄盼盼张有禄胡凯齐静波张岱南程亮 School of Electronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu 611731China State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengdu 611731China School of Physics University of Electronic Science and Technology of ChinaChengdu 611731China

We measure the time-resolved terahertz spectroscopy of GeSn thin film and studied the ultrafast dynamics of its photo-generated *** experimental results show that there are photo-generated carriers in GeSn under femtosecond laser excitation at 2500 nm,and its pump-induced photoconductivity can be explained by the Drude–Smith *** carrier recombination process is mainly dominated by defect-assisted Auger processes and defect *** firstand second-order recombination rates are obtained by the rate equation fitting,which are(2.6±1.1)×10^(-2)ps^(-1)and(6.6±1.8)×10^(-19)cm^(3)·ps^(-1),***,we also obtain the diffusion length of photo-generated carriers in GeSn,which is about 0.4μm,and it changes with the pump delay *** results are important for the GeSn-based infrared optoelectronic devices,and demonstrate that Ge Sn materials can be applied to high-speed optoelectronic detectors and other applications.

关键词： GeSn thin film time-resolved THz spectroscopy ultrafast dynamics carrier recombination

Channel-Resolved ultrafast Dissociation dynamics of NO2 Molecules Studied via Femtosecond Time-Resolved Ion Imaging

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Chinese Journal of Chemical Physics 2019年第3期32卷 292-298,I0001页

作者： Qin-xin Wang Dan-dan Shi Jun-feng Zhang Xue Wang Yu Si Chun-bin Gao Jian Fang Si-zuo Luo College of Electrical Engineering Jilin Engineering Normal UniversityChangchun 130012China Institute of Atomic and Molecular Physics and Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy Jilin UniversityChangchun 130012China

The ultrafast dissociation dynamics of NO2 molecules was investigated by femtosecond laser pump-probe mass spectra and ion *** results show that the kinetic energy release of NO+ions has two components,0.05 eV and 0.25 eV,and the possible dissociation channels have been *** channel resolved transient measurement of NO^+provides a method to disentangle the contribution of ultrafast dissociation pathways,and the transient curves of NO^+ions at different kinetic energy release are fitted by a biexponential *** fast component with a decay time of 0.25 ps is generated from the evolution of Rydberg *** slow component is generated from two competitive channels,one of the channel is absorbing one 400nm photon to the excited state A^2B2,which has a decay time of 30.0ps,and the other slow channel is absorbing three 400nm photons to valence type Rydberg states which have a decay time less than *** channel and time resolved experiment present the potential of sorting out the complex ultrafast dissociation dynamics of molecules.

关键词： ultrafast dynamics Strong field ionization Photodissociation dynamic Velocity map imaging

Photo-Induced ultrafast Electron dynamics in Anatase and Rutile TiO_(2):Effects of Electron-Phonon Interaction

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Chinese Journal of Chemical Physics 2022年第2期35卷 270-280,I0005,I0006,I0001,I0002页

作者： Man Lian Yu-Chen Wang Shiping Peng Yi Zhao State Key Laboratory of Physical Chemistry of Solid Surfaces Fujian Provincial Key Lab of Theoretical and Computational Chemistryand College of Chemistry and Chemical EngineeringXiamen UniversityXiamen 361005China

The photo-induced ultrafast electron dynamics in both anatase and rutile TiO_(2) are investigated by using the Boltzmann transport equation with the explicit incorporation of electron-phonon scattering *** structural parameters required for dynamic simulations are obtained from ab initio *** results show that although the longitudinal optical modes significantly affect the electron energy relaxation dynamics in both phases due to strong Fr?hlich-type couplings,the detailed relaxation mechanisms have obvious *** the case of a single band,the energy relaxation time in anatase is 24.0 fs,twice longer than 11.8 fs in *** discrepancy is explained by the different diffusion distributions over the electronic Bloch states and different scattering contributions from acoustic modes in the two *** for the multiple-band situation involving the lowest six conduction bands,the predicted overall relaxation times are about 47 fs and 57 fs in anatase and rutile,respectively,very different from the case of the single *** slower relaxation in rutile is attributed to the existence of multiple rate-controlled steps during the dynamic *** present findings may be helpful to control the electron dynamics for designing efficient TiO_(2)-based devices.

关键词： Titanium dioxide Electron-phonon interaction ultrafast dynamics Boltzmann transport equation