We describe a collinear velocity-map photoelectron imaging spectrometer, which combines a Wiley-McLaren time-of-flight mass analyzer with a dual-valve laser vaporization source for investigating size-selected cluster ...We describe a collinear velocity-map photoelectron imaging spectrometer, which combines a Wiley-McLaren time-of-flight mass analyzer with a dual-valve laser vaporization source for investigating size-selected cluster and reaction intermediate anions. To generate the reaction anions conveniently, two pulsed valves and a reaction channel are employed instead of premixing carrier gas. The collinear photoelectron imaging spectrometer adopts modified velocity-map electrostatic lens, and provides kinetic energy resolution better than 3%. The performance of the instrument is demonstrated on the photodetachment of Si4^- at 532 and 355 nm, and SiaC^- at 532 nm, respectively. In both cases, photoelectron spectra and anisotropy parameters are obtained from the images. For Si4^-, the spectra show two well- resolved vibrational progressions which correspond to the ground state and the first excited state of the neutral Si4 with peak spacing of 330 and 312 cm^-1, respectively. Preliminary results suggest that the apparatus is a powerful tool for characterizing the electronic structure and photodetachment dynamics of cluster anions.展开更多
The photochemical reaction of potassium ferrocyanide(K_(4)Fe(CN)_(6))exhibits excitation wavelength dependence and non-Kasha rule behavior.In this study,the excited-state dynamics of K_(4)Fe(CN)_(6) were studied by tr...The photochemical reaction of potassium ferrocyanide(K_(4)Fe(CN)_(6))exhibits excitation wavelength dependence and non-Kasha rule behavior.In this study,the excited-state dynamics of K_(4)Fe(CN)_(6) were studied by transient absorption spectroscopy.Excited state electron detachment(ESED)and photoaquation reactions were clarified by comparing the results of 260,320,340,and 350 nm excitations.ESED is the path to generate a hydrated electron(e^(−)_(aq)).ESED energy barrier varies with the excited state,and it occurs even at the first singlet excited state(^(1)T_(1g)).The ^(1)T_(1g) state shows∼0.2 ps lifetime and converts into triplet[Fe(CN)_(6)]4−by intersystem crossing.Subsequently,3Fe(CN)_(5)]^(3-)appears after one CN−ligand is ejected.In sequence,H2O attacksFe(CN)_(5)]^(3-)to generate[Fe(CN)_(5)H_(2)O]^(3−)with a time constant of approximately 20 ps.The ^(1)T_(1g) state and e−aq exhibit strong reducing power.The addition of uridine 5′-monophosphate(UMP)to the K_(4)Fe(CN)_(6) solution decrease the yield of e−aq and reduce the lifetimes of the e−aq and ^(1)T_(1g) state.The obtained reaction rate constant of ^(1)T_(1g) state and UMP is 1.7×10^(14)(mol/L)^(−1)·s^(−1),and the e−aq attachment to UMP is∼8×10^(9)(mol/L)^(−1)·s^(−1).Our results indicate that the reductive damage of K_(4)Fe(CN)_(6) solution to nucleic acids under ultraviolet irradiation cannot be neglected.展开更多
基金ACKNOWLEDGMENTS We thank Professor Hai-yang Li for simulation electron trajectory, and H. Reisler for providing the image analysis software. This work was supported by the National Natural Science Foundation of China （No.20773126）, the Ministry of Science and Technology of China, and the Chinese Academy of Sciences.
文摘We describe a collinear velocity-map photoelectron imaging spectrometer, which combines a Wiley-McLaren time-of-flight mass analyzer with a dual-valve laser vaporization source for investigating size-selected cluster and reaction intermediate anions. To generate the reaction anions conveniently, two pulsed valves and a reaction channel are employed instead of premixing carrier gas. The collinear photoelectron imaging spectrometer adopts modified velocity-map electrostatic lens, and provides kinetic energy resolution better than 3%. The performance of the instrument is demonstrated on the photodetachment of Si4^- at 532 and 355 nm, and SiaC^- at 532 nm, respectively. In both cases, photoelectron spectra and anisotropy parameters are obtained from the images. For Si4^-, the spectra show two well- resolved vibrational progressions which correspond to the ground state and the first excited state of the neutral Si4 with peak spacing of 330 and 312 cm^-1, respectively. Preliminary results suggest that the apparatus is a powerful tool for characterizing the electronic structure and photodetachment dynamics of cluster anions.
基金supported by the National Natural Science Foundation of China(No.21873100 and No.21773226)the Open Fund of the State Key Laboratory of Molecular Reaction Dynamics in Dalian Institute of Chemical Physics,Chinese Academy of Sciences。
文摘The photochemical reaction of potassium ferrocyanide(K_(4)Fe(CN)_(6))exhibits excitation wavelength dependence and non-Kasha rule behavior.In this study,the excited-state dynamics of K_(4)Fe(CN)_(6) were studied by transient absorption spectroscopy.Excited state electron detachment(ESED)and photoaquation reactions were clarified by comparing the results of 260,320,340,and 350 nm excitations.ESED is the path to generate a hydrated electron(e^(−)_(aq)).ESED energy barrier varies with the excited state,and it occurs even at the first singlet excited state(^(1)T_(1g)).The ^(1)T_(1g) state shows∼0.2 ps lifetime and converts into triplet[Fe(CN)_(6)]4−by intersystem crossing.Subsequently,3Fe(CN)_(5)]^(3-)appears after one CN−ligand is ejected.In sequence,H2O attacksFe(CN)_(5)]^(3-)to generate[Fe(CN)_(5)H_(2)O]^(3−)with a time constant of approximately 20 ps.The ^(1)T_(1g) state and e−aq exhibit strong reducing power.The addition of uridine 5′-monophosphate(UMP)to the K_(4)Fe(CN)_(6) solution decrease the yield of e−aq and reduce the lifetimes of the e−aq and ^(1)T_(1g) state.The obtained reaction rate constant of ^(1)T_(1g) state and UMP is 1.7×10^(14)(mol/L)^(−1)·s^(−1),and the e−aq attachment to UMP is∼8×10^(9)(mol/L)^(−1)·s^(−1).Our results indicate that the reductive damage of K_(4)Fe(CN)_(6) solution to nucleic acids under ultraviolet irradiation cannot be neglected.
