Pyrolysis of benzene at 30 Torr was studied from 1360 K to 1820 K in this work. Synchrotron vacuum ultraviolet photoionization mass spectrometry was employed to detect the pyroly- sis products such as radicals, isomer...Pyrolysis of benzene at 30 Torr was studied from 1360 K to 1820 K in this work. Synchrotron vacuum ultraviolet photoionization mass spectrometry was employed to detect the pyroly- sis products such as radicals, isomers and polycyclic aromatic hydrocarbons, and measure their mole fraction profiles versus temperature. A low-pressure pyrolysis model of benzene was developed and validated by the experimental results. Rate of production analysis was performed to reveal the major reaction networks in both fuel decomposition and aromatic growth processes. It is concluded that benzene is mainly decomposed via H-abstraction reaction to produce phenyl and partly decomposed via unimolecular decomposition reac- tions to produce propargyl or phenyl. The decomposition process stops at the formation of acetylene and polyyne species like diacetylene and 1,3,5-hexatriyne due to their high thermal stabilities. Besides, the aromatic growth process in the low-pressure pyrolysis of benzene is concluded to initiate from benzene and phenyl, and is controlled by the even carbon growth mechanism due to the inhibited formation of C5 and C7 species which play important roles in the odd carbon growth mechanism.展开更多
Strained Si_ 1-xGe_x and Si materials are successfully grown on Si substrate by ultraviolet light chemical vapor deposition under ultrahigh vacuum at a low substrate temperature of 450℃ and 480℃,respectively.At such...Strained Si_ 1-xGe_x and Si materials are successfully grown on Si substrate by ultraviolet light chemical vapor deposition under ultrahigh vacuum at a low substrate temperature of 450℃ and 480℃,respectively.At such low temperature,autodoping effects from the substrate and interdiffusion effects at each interface could be suppressed efficiently.The strained Si_ 1-xGe_x and multilayer Si_ 1-xGe_x/Si structures are examined by X-ray diffraction,SMIS,etc.,and it is found that the materials have good crystallinity and the rising and falling edges are steep.The technique has a capability of growing high-quality Si_ 1-xGe_x/Si strained layers.展开更多
Infrared-vacuum ultraviolet （IR-VUV） spectra of neutral trimethylamine dimer were mea- sured in the 2500-3800 cm-1 region. Quantum chemical calculations were performed to identify the structure of the low-lying isom...Infrared-vacuum ultraviolet （IR-VUV） spectra of neutral trimethylamine dimer were mea- sured in the 2500-3800 cm-1 region. Quantum chemical calculations were performed to identify the structure of the low-lying isomers and to assign the observed spectral features. The bands at 2975 and 2949 cm-1 were assigned to the antisymmetric C-H stretching and the band at 2823 cm-1 to the symmetric C-H stretching, respectively. The 2739 cm-1 band was due to the CH3 bending overtone, which disappeared at low IR laser power of 1 mJ/mm2. The extra band at 2773 cm-1 could be due to Fermi resonance behavior of the light isotopologue, these are often close in energy and can strongly mix through cubic terms in the potential function. Experimental and theoretical results indicate the likely coexistence of multiple structures. The peak widths of IR spectra of neutral trimethylamine dimer are not significantly affected by the structural transformation, allowing the stretching modes to be well resolved.展开更多
基金This work is supported by the National Natu- ral Science Foundation of China （No.51106146 and No.51036007）, China Postdoctoral Science Foundation （No.20100480047 and No.201104326）, Chinese Univer- sities Scientific Fund （No.WK2310000010）, and Chinese Academy of Sciences.
文摘Pyrolysis of benzene at 30 Torr was studied from 1360 K to 1820 K in this work. Synchrotron vacuum ultraviolet photoionization mass spectrometry was employed to detect the pyroly- sis products such as radicals, isomers and polycyclic aromatic hydrocarbons, and measure their mole fraction profiles versus temperature. A low-pressure pyrolysis model of benzene was developed and validated by the experimental results. Rate of production analysis was performed to reveal the major reaction networks in both fuel decomposition and aromatic growth processes. It is concluded that benzene is mainly decomposed via H-abstraction reaction to produce phenyl and partly decomposed via unimolecular decomposition reac- tions to produce propargyl or phenyl. The decomposition process stops at the formation of acetylene and polyyne species like diacetylene and 1,3,5-hexatriyne due to their high thermal stabilities. Besides, the aromatic growth process in the low-pressure pyrolysis of benzene is concluded to initiate from benzene and phenyl, and is controlled by the even carbon growth mechanism due to the inhibited formation of C5 and C7 species which play important roles in the odd carbon growth mechanism.
文摘Strained Si_ 1-xGe_x and Si materials are successfully grown on Si substrate by ultraviolet light chemical vapor deposition under ultrahigh vacuum at a low substrate temperature of 450℃ and 480℃,respectively.At such low temperature,autodoping effects from the substrate and interdiffusion effects at each interface could be suppressed efficiently.The strained Si_ 1-xGe_x and multilayer Si_ 1-xGe_x/Si structures are examined by X-ray diffraction,SMIS,etc.,and it is found that the materials have good crystallinity and the rising and falling edges are steep.The technique has a capability of growing high-quality Si_ 1-xGe_x/Si strained layers.
文摘Infrared-vacuum ultraviolet （IR-VUV） spectra of neutral trimethylamine dimer were mea- sured in the 2500-3800 cm-1 region. Quantum chemical calculations were performed to identify the structure of the low-lying isomers and to assign the observed spectral features. The bands at 2975 and 2949 cm-1 were assigned to the antisymmetric C-H stretching and the band at 2823 cm-1 to the symmetric C-H stretching, respectively. The 2739 cm-1 band was due to the CH3 bending overtone, which disappeared at low IR laser power of 1 mJ/mm2. The extra band at 2773 cm-1 could be due to Fermi resonance behavior of the light isotopologue, these are often close in energy and can strongly mix through cubic terms in the potential function. Experimental and theoretical results indicate the likely coexistence of multiple structures. The peak widths of IR spectra of neutral trimethylamine dimer are not significantly affected by the structural transformation, allowing the stretching modes to be well resolved.
