The photoionization and photodissociation of 1,4-dioxane have been investigated with a reflectron time-of-flight photoionization mass spectrometry and a tunable vacuum ultraviolet synchrotron radiation in the energy r...The photoionization and photodissociation of 1,4-dioxane have been investigated with a reflectron time-of-flight photoionization mass spectrometry and a tunable vacuum ultraviolet synchrotron radiation in the energy region of 8.0-15.5 eV. Parent ion and fragment ions at m/z 88, 87, 58, 57, 45, 44, 43, 41, 31, 30, 29, 28 and 15 are detected under supersonic conditions. The ionization energy of DX as well as the appearance energies of its fragment ions C4H7O2^＋, C3H6O^＋, C3H5O^＋, C2H5O^＋, C2H4O^＋, C2H3O^＋, C3H5^＋, CH3O^＋, C2H6^＋, C2H5^＋/CHO^＋, C2H4^＋ and CH3^＋ was determined from their photoionization efficiency curves. The optimized structures for the neutrals, cations, transition states and intermediates related to photodissociation of DX are characterized at the B3LYP/6-31＋G（d,p） level and their energies are obtained by G3B3 method. Possible dissociative channels of the DX are proposed based on comparison of experimental AE values and theoretical predicted ones. Intramolecular hydrogen migrations are found to be the dominant processes in most of the fragmentation pathways of 1,4-dioxane.展开更多
Dissociative photoionization of 1,2-epoxyoctane was investigated by synchrotron radiation vacuum ultraviolet photons in the energy region of 9.8-16.6 eV under ultrasonic molec-ular beam. Dissociative fragment ions wer...Dissociative photoionization of 1,2-epoxyoctane was investigated by synchrotron radiation vacuum ultraviolet photons in the energy region of 9.8-16.6 eV under ultrasonic molec-ular beam. Dissociative fragment ions were measured with reffection time-of-ight mass spectrometer at di erent photon energies. Appearance potentials of the dominative ion fragments were determined through photoionization efficiency curves. The structures and energies of the parent, ionized and neutral radicals were obtained with G3 calculations. Through comparing the experimental results with the theoretical calculations, we proposed the dissociative channels for the photoionization of 1,2-epoxyoctane.展开更多
Theoretical calculations have been carried out to investigate the possible dissociation channels of isoprene. We focus on the major fragment ions of C5H7＋, C5H5＋, C4H5＋, C3H6＋, C3H5＋, C3H4＋, C3H3＋ and C2H3＋, w...Theoretical calculations have been carried out to investigate the possible dissociation channels of isoprene. We focus on the major fragment ions of C5H7＋, C5H5＋, C4H5＋, C3H6＋, C3H5＋, C3H4＋, C3H3＋ and C2H3＋, which were observed experimentally from the isoprene dissociative photoionization. The energy calculations were performed with the CBS-QB3 model. All the geometries and energies of the fragments, intermediates and transition states involved in the dissociations channels were determined. Finally, the mechanisms of the dissociation pathways were discussed on the comparison of theoretical and experimental results.展开更多
The binary cluster ions Ge2Cn+/Ge2Cn? and GeCn+ have been produced by laser ablation. The parity ef- fect is present in the negative ions Ge2Cn?, though it is not very prominent. While the experiments tell that the pa...The binary cluster ions Ge2Cn+/Ge2Cn? and GeCn+ have been produced by laser ablation. The parity ef- fect is present in the negative ions Ge2Cn?, though it is not very prominent. While the experiments tell that the parity effect is totally not shown in the positive ions Ge2Cn+. An extensive theoretical investigation on GeCn/GeCn+/GeCn?(n = 1?10) and Ge2Cn/Ge2Cn+/Ge2Cn?(n = 1?9) has been carried out by density functional theory at B3LPY level. The calcula- tion shows that the low-lying states of GeCn/GeCn+/GeCn?(n = 1?10) and Ge2Cn/Ge2Cn+/Ge2Cn? (n = 1?9) are linear structure with germanium atoms locating at terminals respectively. The electronic distributions, ionization potential (IPad), elec- tron affinity (EA) and increasing bonding energy reveal that the parity effect of neutral species is much stronger than that of ions, which is attributed to the valence π-electrons. It is explained that the differences between experiments and cal- culations are due to the kinetic factor in the formation of Ge2Cn±.展开更多
Photoionization/dissociation of 1,2 propylene oxide are performed by using a time of flight mass spectrometer(TOF MS) with vacuum ultraviolet photons from Hefei synchrotron radiation source. The photoionization TOF ma...Photoionization/dissociation of 1,2 propylene oxide are performed by using a time of flight mass spectrometer(TOF MS) with vacuum ultraviolet photons from Hefei synchrotron radiation source. The photoionization TOF mass spectrum and photoionization efficiency(PIE) curves of fragment ions are measured.The appearance potentials(AP) of these ions are obtained from their PIE curves. From these data, the formation enthalpies of the observed ions have been evaluated, and their possible channels have been analyzed. The mechanism of dissociative photoionization of 1,2 propylene oxide has been discussed.展开更多
基金This work was supported by the National Natural Science Foundation of China （No.91544105, No.U1532137, No.11575178, and No.U1232209）.
文摘The photoionization and photodissociation of 1,4-dioxane have been investigated with a reflectron time-of-flight photoionization mass spectrometry and a tunable vacuum ultraviolet synchrotron radiation in the energy region of 8.0-15.5 eV. Parent ion and fragment ions at m/z 88, 87, 58, 57, 45, 44, 43, 41, 31, 30, 29, 28 and 15 are detected under supersonic conditions. The ionization energy of DX as well as the appearance energies of its fragment ions C4H7O2^＋, C3H6O^＋, C3H5O^＋, C2H5O^＋, C2H4O^＋, C2H3O^＋, C3H5^＋, CH3O^＋, C2H6^＋, C2H5^＋/CHO^＋, C2H4^＋ and CH3^＋ was determined from their photoionization efficiency curves. The optimized structures for the neutrals, cations, transition states and intermediates related to photodissociation of DX are characterized at the B3LYP/6-31＋G（d,p） level and their energies are obtained by G3B3 method. Possible dissociative channels of the DX are proposed based on comparison of experimental AE values and theoretical predicted ones. Intramolecular hydrogen migrations are found to be the dominant processes in most of the fragmentation pathways of 1,4-dioxane.
文摘Dissociative photoionization of 1,2-epoxyoctane was investigated by synchrotron radiation vacuum ultraviolet photons in the energy region of 9.8-16.6 eV under ultrasonic molec-ular beam. Dissociative fragment ions were measured with reffection time-of-ight mass spectrometer at di erent photon energies. Appearance potentials of the dominative ion fragments were determined through photoionization efficiency curves. The structures and energies of the parent, ionized and neutral radicals were obtained with G3 calculations. Through comparing the experimental results with the theoretical calculations, we proposed the dissociative channels for the photoionization of 1,2-epoxyoctane.
基金This work was supported by the National Natural Science Foundation of China （No.91544228, No.21307137, No.41575125, No.41375127, No.U1232209） and the Outstanding Youth Science Foundation of Fujian Province of China （No.2015J06009）.
文摘Theoretical calculations have been carried out to investigate the possible dissociation channels of isoprene. We focus on the major fragment ions of C5H7＋, C5H5＋, C4H5＋, C3H6＋, C3H5＋, C3H4＋, C3H3＋ and C2H3＋, which were observed experimentally from the isoprene dissociative photoionization. The energy calculations were performed with the CBS-QB3 model. All the geometries and energies of the fragments, intermediates and transition states involved in the dissociations channels were determined. Finally, the mechanisms of the dissociation pathways were discussed on the comparison of theoretical and experimental results.
基金supported by the National Natural Science Foundation of China(Grant No.20302020)
文摘The binary cluster ions Ge2Cn+/Ge2Cn? and GeCn+ have been produced by laser ablation. The parity ef- fect is present in the negative ions Ge2Cn?, though it is not very prominent. While the experiments tell that the parity effect is totally not shown in the positive ions Ge2Cn+. An extensive theoretical investigation on GeCn/GeCn+/GeCn?(n = 1?10) and Ge2Cn/Ge2Cn+/Ge2Cn?(n = 1?9) has been carried out by density functional theory at B3LPY level. The calcula- tion shows that the low-lying states of GeCn/GeCn+/GeCn?(n = 1?10) and Ge2Cn/Ge2Cn+/Ge2Cn? (n = 1?9) are linear structure with germanium atoms locating at terminals respectively. The electronic distributions, ionization potential (IPad), elec- tron affinity (EA) and increasing bonding energy reveal that the parity effect of neutral species is much stronger than that of ions, which is attributed to the valence π-electrons. It is explained that the differences between experiments and cal- culations are due to the kinetic factor in the formation of Ge2Cn±.
文摘Photoionization/dissociation of 1,2 propylene oxide are performed by using a time of flight mass spectrometer(TOF MS) with vacuum ultraviolet photons from Hefei synchrotron radiation source. The photoionization TOF mass spectrum and photoionization efficiency(PIE) curves of fragment ions are measured.The appearance potentials(AP) of these ions are obtained from their PIE curves. From these data, the formation enthalpies of the observed ions have been evaluated, and their possible channels have been analyzed. The mechanism of dissociative photoionization of 1,2 propylene oxide has been discussed.
