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
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.
