A new velocity map imaging spectrometer is constructed for molecular reaction dynamics studies using time-resolved photoelectron/ion spectroscopy method. By combining a kHz pulsed valve and an ICCD camera, this veloci...A new velocity map imaging spectrometer is constructed for molecular reaction dynamics studies using time-resolved photoelectron/ion spectroscopy method. By combining a kHz pulsed valve and an ICCD camera, this velocity map imaging spectrometer can be run at a repetition rate of 1 kHz, totally compatible with the fs Ti：Sapphire laser system, facilitating time-resolved studies in gas phase which are usually time-consuming. Time-resolved velocity map imaging study of NH3 photodissociation at 200 nm was performed and the time-resolved total kinetic energy release spectrum of H＋NH~ products provides rich information about the dissociation dynamics of NH3. These results show that this new apparatus is a powerful tool for investigating the molecular reaction dynamics using time-resolved methods.展开更多
The ultrafast dynamics of water molecules excited to the two F states is studied by combining two-photon excitation and time-resolved photoelectron imaging techniques. The lifetimes of the F1A1 and F1B1 states of H2O ...The ultrafast dynamics of water molecules excited to the two F states is studied by combining two-photon excitation and time-resolved photoelectron imaging techniques. The lifetimes of the F1A1 and F1B1 states of H2O (D2O) were derived to be 1.0±0.3 (1.9±0.4) and 10±3 (30±10) ps, respectively. We propose that the F1A1 state mainly decays through the D state, due to the nonadiabatic coupling between them, while the F1B1 state decays through the F1A1 state via Coriolis interaction.展开更多
The S_(1) state decay dynamics of 2-hydroxypyridine following UV excitation at a wavelength range of 276.9-250.0 nm is investigated using femtosecond time-resolved photoelectron imaging technique.Based on pump wavelen...The S_(1) state decay dynamics of 2-hydroxypyridine following UV excitation at a wavelength range of 276.9-250.0 nm is investigated using femtosecond time-resolved photoelectron imaging technique.Based on pump wavelength dependence of the decay dynamics,a refined decay picture is proposed.At pump wavelength of 276.9 nm,the S_(1) state is depopulated through intersystem crossing to lower triplet state(s).At 264.0 nm,both intersystem crossing to lower triplet state(s)and internal conversion to the ground state are in operation.At 250.0 nm,internal conversion to the ground state becomes dominated.展开更多
The intra- and inter-band relaxation dynamics of CdSe/CdS/ZnS core/shell/shell quantum dots are investigated with the aid of time-resolved nonlinear transmission spectra which are obtained using femtosecond pump-probe...The intra- and inter-band relaxation dynamics of CdSe/CdS/ZnS core/shell/shell quantum dots are investigated with the aid of time-resolved nonlinear transmission spectra which are obtained using femtosecond pump-probe technique. By selectively exciting the core and shell carrier, the dynamics are studied in detail. Carrier relaxation is found faster in the conduction band of the CdS shell （about 130 fs） than that in the conduction band of the CdSe core （about 400 fs）. From the experiments it is distinctly demonstrated the existence of the defect states in the interface between the CdSe core and the CdS shell, indicating that ultrafast spectroscopy might be a suitable tool in studying interface and surface morphology properties in nanosystems.展开更多
基金This work was supported by the National Basic Research Program of China （No.2013CB922200）, the Ministry of Science and Technology of China （No.2012YQ12004704）, and the National Natural Science Foundation of China （No.21573228）.
文摘A new velocity map imaging spectrometer is constructed for molecular reaction dynamics studies using time-resolved photoelectron/ion spectroscopy method. By combining a kHz pulsed valve and an ICCD camera, this velocity map imaging spectrometer can be run at a repetition rate of 1 kHz, totally compatible with the fs Ti：Sapphire laser system, facilitating time-resolved studies in gas phase which are usually time-consuming. Time-resolved velocity map imaging study of NH3 photodissociation at 200 nm was performed and the time-resolved total kinetic energy release spectrum of H＋NH~ products provides rich information about the dissociation dynamics of NH3. These results show that this new apparatus is a powerful tool for investigating the molecular reaction dynamics using time-resolved methods.
基金supported by the National Natural Science Foundation of China (No.21573228, No.21833003, No.21673232, and No.21773236)the Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDB17000000)
文摘The ultrafast dynamics of water molecules excited to the two F states is studied by combining two-photon excitation and time-resolved photoelectron imaging techniques. The lifetimes of the F1A1 and F1B1 states of H2O (D2O) were derived to be 1.0±0.3 (1.9±0.4) and 10±3 (30±10) ps, respectively. We propose that the F1A1 state mainly decays through the D state, due to the nonadiabatic coupling between them, while the F1B1 state decays through the F1A1 state via Coriolis interaction.
基金supported by the National Natural Science Foundation of China(No.21833003)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB17000000)the Key Technology Team of the Chinese Academy of Sciences(GJJSTD20190002)。
文摘The S_(1) state decay dynamics of 2-hydroxypyridine following UV excitation at a wavelength range of 276.9-250.0 nm is investigated using femtosecond time-resolved photoelectron imaging technique.Based on pump wavelength dependence of the decay dynamics,a refined decay picture is proposed.At pump wavelength of 276.9 nm,the S_(1) state is depopulated through intersystem crossing to lower triplet state(s).At 264.0 nm,both intersystem crossing to lower triplet state(s)and internal conversion to the ground state are in operation.At 250.0 nm,internal conversion to the ground state becomes dominated.
基金This work was supported by the National Natural Science Foundation of China （No.11074003） and the Key Program of Educational Commission of Anhui Province of China （No.KJ2010AI32）. For the help of Prof. J. L. Zhao at Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences in sample preparation is greatly appreciated.
文摘The intra- and inter-band relaxation dynamics of CdSe/CdS/ZnS core/shell/shell quantum dots are investigated with the aid of time-resolved nonlinear transmission spectra which are obtained using femtosecond pump-probe technique. By selectively exciting the core and shell carrier, the dynamics are studied in detail. Carrier relaxation is found faster in the conduction band of the CdS shell （about 130 fs） than that in the conduction band of the CdSe core （about 400 fs）. From the experiments it is distinctly demonstrated the existence of the defect states in the interface between the CdSe core and the CdS shell, indicating that ultrafast spectroscopy might be a suitable tool in studying interface and surface morphology properties in nanosystems.
