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 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 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
3-Furfural(C_(5)H_(4)O_(2))is a furan(C_(4)H_(4)O)derivative compound formed by replacing the hydrogen(H)atom at the ring 3-position with the aldehyde(CHO)group substituent.In this work,we intend to investigate the ul...3-Furfural(C_(5)H_(4)O_(2))is a furan(C_(4)H_(4)O)derivative compound formed by replacing the hydrogen(H)atom at the ring 3-position with the aldehyde(CHO)group substituent.In this work,we intend to investigate the ultrafast decay dynamics of electronically excited 3-furfural using the femtosecond time-resolved photoelectron imaging technique.At pump wavelengths of 259.5,238.6 and 218.311m,two alternative decay mechanisms for the S_(2)(^(1)ππ*)state are tentatively proposed and discussed.Specifically,we prefer to suggest that a fraction of the initially prepared wavepacket in the S_(2)(^(1)ππ*)state is likely to undergo the subpicosecond relaxation via the S_(1)(^(1)nπ*)state.Presumably the lower lying T_(2)(^(3)ππ*)state is subsequently populated on a∼4 ps timescale via intersystem crossing from the minimum of the S_(1)(^(1)nπ*)state surface.The relaxation of the T_(2)(^(3)ππ*)state is sensitive to its vibrational excess energy and the value of its lifetime is 1.6±0.2 ns,280±30 ps and 50±10 ps for pump wavelengths of 259.5,238.6 and 218.3 m,respectively.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.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.22203095,No.22103087,and No.22288201)the State Key Laboratory of Molecular Reaction Dynamics(SKLMRDZ202406)the Chinese Academy of Sciences(GJJSTD20220001).
文摘3-Furfural(C_(5)H_(4)O_(2))is a furan(C_(4)H_(4)O)derivative compound formed by replacing the hydrogen(H)atom at the ring 3-position with the aldehyde(CHO)group substituent.In this work,we intend to investigate the ultrafast decay dynamics of electronically excited 3-furfural using the femtosecond time-resolved photoelectron imaging technique.At pump wavelengths of 259.5,238.6 and 218.311m,two alternative decay mechanisms for the S_(2)(^(1)ππ*)state are tentatively proposed and discussed.Specifically,we prefer to suggest that a fraction of the initially prepared wavepacket in the S_(2)(^(1)ππ*)state is likely to undergo the subpicosecond relaxation via the S_(1)(^(1)nπ*)state.Presumably the lower lying T_(2)(^(3)ππ*)state is subsequently populated on a∼4 ps timescale via intersystem crossing from the minimum of the S_(1)(^(1)nπ*)state surface.The relaxation of the T_(2)(^(3)ππ*)state is sensitive to its vibrational excess energy and the value of its lifetime is 1.6±0.2 ns,280±30 ps and 50±10 ps for pump wavelengths of 259.5,238.6 and 218.3 m,respectively.
