Browsing by Author "Chen, Jin-Dah"

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Infrared absorption of CH(3)OSO detected with time-resolved Fourier-transform spectroscopy
(2011-03-07)
Chen, Jin-Dah
;
Lee, Yuan-Pern
;
應用化學系
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應用化學系分子科學碩博班
;
Department of Applied Chemistry
A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to detect temporally resolved infrared absorption spectra of CH(3)OSO produced upon irradiation of a flowing gaseous mixture of CH(3)OS(O)Cl in N(2) or CO(2) at 248 nm. Two intense transient features with origins near 1152 and 994 cm(-1) are assigned to syn-CH(3)OSO; the former is attributed to overlapping bands at 1154 +/- 3 and 1151 +/- 3 cm(-1), assigned to the S=O stretching mixed with CH(3) rocking (nu(8)) and the S=O stretching mixed with CH(3) wagging (nu(9)) modes, respectively, and the latter to the C-O stretching (nu(10)) mode at 994 +/- 6 cm(-1). Two weak bands at 2991 +/- 6 and 2956 +/- 3 cm(-1) are assigned as the CH(3) antisymmetric stretching (nu(2)) and symmetric stretching (nu(3)) modes, respectively. Observed vibrational transition wavenumbers agree satisfactorily with those predicted with quantum-chemical calculations at level B3P86/aug-cc-pVTZ. Based on rotational parameters predicted at that level, the simulated rotational contours of these bands agree satisfactorily with experimental results. The simulation indicates that the S=O stretching mode of anti-CH(3)OSO near 1164 cm(-1) likely makes a small contribution to the observed band near 1152 cm(-1). A simple kinetic model of self-reaction is employed to account for the decay of CH(3)OSO and yields a second-order rate coefficient k =(4 +/- 2) x 10(-10) cm(3) molecule(-1) s(-1). (C) 2011 American Institute of Physics. [doi: 10.1063/1.3556817]
Infrared absorption of CH3OSO detected with time-resolved Fourier-transform spectroscopy
(2011-03-07)
Chen, Jin-Dah
;
Lee, Yuan-Pern
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to detect temporally resolved infrared absorption spectra of CH3OSO produced upon irradiation of a flowing gaseous mixture of CH3OS(O)Cl in N-2 or CO2 at 248 nm. Two intense transient features with origins near 1152 and 994 cm(-1) are assigned to syn-CH3OSO; the former is attributed to overlapping bands at 1154 +/- 3 and 1151 +/- 3 cm(-1), assigned to the S=O stretching mixed with CH3 rocking (nu(8)) and the S=O stretching mixed with CH3 wagging (nu(9)) modes, respectively, and the latter to the C-O stretching (nu(10)) mode at 994 +/- 6 cm(-1). Two weak bands at 2991 +/- 6 and 2956 +/- 3 cm(-1) are assigned as the CH3 antisymmetric stretching (nu(2)) and symmetric stretching (nu(3)) modes, respectively. Observed vibrational transition wavenumbers agree satisfactorily with those predicted with quantum-chemical calculations at level B3P86/aug-cc-pVTZ. Based on rotational parameters predicted at that level, the simulated rotational contours of these bands agree satisfactorily with experimental results. The simulation indicates that the S=O stretching mode of anti-CH3OSO near 1164 cm(-1) likely makes a small contribution to the observed band near 1152 cm(-1). A simple kinetic model of self-reaction is employed to account for the decay of CH3OSO and yields a second-order rate coefficient k =(4 +/- 2) x 10(-10) cm(3) molecule(-1) s(-1). (C) 2011 American Institute of Physics. [doi: 10.1063/1.3556817]
Infrared absorption of gaseous benzoylperoxy radical C(6)H(5)C(O)OO recorded with a step-scan Fourier-transform spectrometer
(2011-12-14)
Golec, Barbara
;
Chen, Jin-Dah
;
Lee, Yuan-Pern
;
應用化學系
;
應用化學系分子科學碩博班
A step-scan Fourier-transform infrared spectrometer coupled with a multipass absorption cell was utilized to monitor the transient species produced in gaseous reactions of benzoyl radical, C(6)H(5)CO, with O(2). C(6)H(5)CO was produced either from photolysis of acetophenone, C(6)H(5)C(O)CH(3), at 248 nm, or from photolysis of a mixture of benzaldehyde, C(6)H(5)CHO, and Cl(2) at 355 nm. Two intense bands near 1830 and 1226 cm(-1) are assigned to the C=O stretching (nu(6)) and the C-C stretching mixed with C-H deformation (nu(13)) modes, and two weaker bands near 1187 and 1108 cm(-1) are assigned to the nu(14) (C-H deformation) and nu(16) (O-O stretching/C-H deformation) modes of C(6)H(5)C(O)OO, the benzoylperoxy radical. These observed vibrational wave numbers and relative infrared intensities agree with those reported for syn-C(6)H(5)C(O)OO isolated in solid Ar and values predicted for syn-C(6)H(5)C(O)OO with the B3LYP/cc-pVTZ method. The simulated rotational contours of the two intense bands based on rotational parameters predicted with the B3LYP/cc-pVTZ method fit satisfactorily with experimental results. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3664304]
Infrared absorption of gaseous benzoylperoxy radical C6H5C(O)OO recorded with a step-scan Fourier-transform spectrometer
(2011-12-14)
Golec, Barbara
;
Chen, Jin-Dah
;
Lee, Yuan-Pern
;
應用化學系
;
應用化學系分子科學碩博班
A step-scan Fourier-transform infrared spectrometer coupled with a multipass absorption cell was utilized to monitor the transient species produced in gaseous reactions of benzoyl radical, C6H5CO, with O-2. C6H5CO was produced either from photolysis of acetophenone, C6H5C(O)CH3, at 248 nm, or from photolysis of a mixture of benzaldehyde, C6H5CHO, and Cl-2 at 355 nm. Two intense bands near 1830 and 1226 cm(-1) are assigned to the C=O stretching (nu(6)) and the C-C stretching mixed with C-H deformation (nu(13)) modes, and two weaker bands near 1187 and 1108 cm(-1) are assigned to the nu(14) (C-H deformation) and nu(16) (O-O stretching/C-H deformation) modes of C6H5C(O)OO, the benzoylperoxy radical. These observed vibrational wave numbers and relative infrared intensities agree with those reported for syn-C6H5C(O)OO isolated in solid Ar and values predicted for syn-C6H5C(O)OO with the B3LYP/cc-pVTZ method. The simulated rotational contours of the two intense bands based on rotational parameters predicted with the B3LYP/cc-pVTZ method fit satisfactorily with experimental results. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3664304]
Transient Infrared Absorption Spectra of Reaction Intermediates Detected with a Step-scan Fourier-transform Infrared Spectrometer
(2014-01-01)
Huang, Yu-Hsuan
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Chen, Jin-Dah
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Hsu, Kuo-Hsiang
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Chu, Li-Kang
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Lee, Yuan-Pern
Our group has utilized a step-scan FTIR spectrometer operating in the absorption mode to characterize transient species in chemical reactions upon photo-irradiation of gaseous mixtures in a multipass White cell. The operational temporal resolution is typically 1-10 s with spectral resolution 0.1-4 cm(-1), depending on conditions. The acquisition of both ac- and dc-coupled signals enables an extraction of minute changes in the large background signal to attain a typical detectable absorbance variation greater than 1 x 10(-4). By consideration of reaction mechanisms and comparison of vibrational wavenumbers, IR intensities, and rotational contours predicted with theoretical calculations, we have assigned IR absorption bands of many important atmospheric free radicals and unstable species including their conformers, such as ClCO, ClSO, ClCS, ClCOOH, CH3SO2, CH3SOO, CH3OSO, CH3SO, CH3OO, CH3C(O)OO, CH2OO C6H5CO, C6H5SO2, and C6H5C(O)OO. The advantages and limitations of this technique to perform spectral and kinetic investigations of transient species in chemical reactions are discussed.