Infrared absorption of CH 3 OSO detected with time-resolved Fourier-transform spectroscopy

Kong

The Journal of Chemical Physics

2012

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Irradiation at 239 ± 20 nm of a p-H(2) matrix containing methoxysulfinyl chloride, CH(3)OS(O)Cl, at 3.2 K with filtered light from a medium-pressure mercury lamp produced infrared (IR) absorption lines at 3028.4 (attributable to ν(1), CH(2) antisymmetric stretching), 2999.5 (ν(2), CH(3) antisymmetric stretching), 2950.4 (ν(3), CH(3) symmetric stretching), 1465.2 (ν(4), CH(2) scissoring), 1452.0 (ν(5), CH(3) deformation), 1417.8 (ν(6), CH(3) umbrella), 1165.2 (ν(7), CH(3) wagging), 1152.1 (ν(8), S=O stretching mixed with CH(3) rocking), 1147.8 (ν(9), S=O stretching mixed with CH(3) wagging), 989.7 (ν(10), C-O stretching), and 714.5 cm(-1) (ν(11), S-O stretching) modes of syn-CH(3)OSO. When CD(3)OS(O)Cl in a p-H(2) matrix was used, lines at 2275.9 (ν(1)), 2251.9 (ν(2)), 2083.3 (ν(3)), 1070.3 (ν(4)), 1056.0 (ν(5)), 1085.5 (ν(6)), 1159.7 (ν(7)), 920.1 (ν(8)), 889.0 (ν(9)), 976.9 (ν(10)), and 688.9 (ν(11)) cm(-1) appeared and are assigned to syn-CD(3)OSO; the mode numbers correspond to those used for syn-CH(3)OSO. The assignments are based on the photolytic behavior and a comparison of observed vibrational wavenumbers, infrared intensities, and deuterium isotopic shifts with those predicted with the B3P86∕aug-cc-pVTZ method. Our results extend the previously reported four transient IR absorption bands of gaseous syn-CH(3)OSO near 2991, 2956, 1152, and 994 cm(-1) to 11 lines, including those associated with C-O, O-S, and S=O stretching modes. Vibrational wavenumbers of syn-CD(3)OSO are new. These results demonstrate the advantage of a diminished cage effect of solid p-H(2) such that the Cl atom, produced via UV photodissociation of CH(3)OS(O)Cl in situ, might escape from the original cage to yield isolated CH(3)OSO radicals.

Section: A Assignments Of Lines In Group a In The Ch 3 Os(o)cl/p-h 2supporting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

Section: Experiments and Computationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

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Infrared absorption of CH3OSO and CD3OSO radicals produced upon photolysis of CH3OS(O)Cl and CD3OS(O)Cl in p-H2 matrices

Kong

The Journal of Chemical Physics

2012

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“…Two bands at 1076 ± 2 and 1280 ± 2 cm −1 were assigned to gaseous CH 3 SO 2 , 26 and two bands at 1154 ± 2 and 994 ± 4 cm −1 were assigned to gaseous CH 3 OSO based on our results using time-resolved FTIR absorption spectroscopy. 48 A band near 1159 cm −1 was tentatively assigned to gaseous CH 3 SO 2 I. 26 There is no information available about ISO 2 or IOSO.…”

Section: Discussionmentioning

confidence: 99%

Infrared absorption of CH3SO2 observed upon irradiation of a p-H2 matrix containing CH3I and SO2

The Journal of Chemical Physics

2011

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Irradiation with a mercury lamp at 254 nm of a p-H(2) matrix containing CH(3)I and SO(2) at 3.3 K, followed by annealing of the matrix, produced prominent features at 633.8, 917.5, 1071.1 (1072.2), 1272.5 (1273.0, 1273.6), and 1416.0 cm(-1), attributable to ν(11) (C-S stretching), ν(10) (CH(3) wagging), ν(8) (SO(2) symmetric stretching), ν(7) (SO(2) antisymmetric stretching), and ν(4) (CH(2) scissoring) modes of methylsulfonyl radical (CH(3)SO(2)), respectively; lines listed in parentheses are weaker lines likely associated with species in a different matrix environment. Further irradiation at 365 nm diminishes these features and produced SO(2) and CH(3). Additional features at 1150.1 and 1353.1 (1352.7) cm(-1) are tentatively assigned to the SO(2) symmetric and antisymmetric stretching modes of ISO(2). These assignments are based on comparison of observed vibrational wavenumbers and (18)O- and (34)S-isotopic shifts with those predicted with the B3P86 method. Our results agree with the previous report of transient IR absorption bands of gaseous CH(3)SO(2) at 1280 and 1076 cm(-1). These results demonstrate that the cage effect of solid p-H(2) is diminished so that CH(3) radicals, produced via UV photodissociation of CH(3)I in situ, might react with SO(2) to form CH(3)SO(2) during irradiation and upon annealing. Observation of CH(3)SO(2) but not CH(3)OSO is consistent with the theoretical predictions that only the former reactions proceed via a barrierless path.

Transient Infrared Absorption Spectra of Reaction Intermediates Detected with a Step‐scan Fourier‐transform Infrared Spectrometer

Huang

Chen

Hsu

et al. 2013

J Chinese Chemical Soc

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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 ms 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 11 0 -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, CH 3 SO 2 , CH 3 SOO, CH 3 OSO, CH 3 SO, CH 3 OO, CH 3 C(O)OO, CH 2 OO C 6 H 5 CO, C 6 H 5 SO 2 , and C 6 H 5 C(O)OO. The advantages and limitations of this technique to perform spectral and kinetic investigations of transient species in chemical reactions are discussed. (2010-). His main research interests focus on the spectroscopy, kinetics, and ion pumps of the photosynthetic proteins, using various time-resolved approaches including step-scan FTIR, nanosecond-resolved transient absorption, and electrochemical methods. Chiao Tung University. The main research topics pursued concern spectroscopy, kinetics and dynamics of free radicals or unstable species, using diverse methods including step-scan time-resolved FTIR (emission or absorption), matrix isolation using p-H 2 , cavity ringdown, IR-VUV photoionization, and ultrafast lasers. He has identified more than 70 new free radicals, most of which are important in atmospheric, combustion, or planetary chemistry. He has received numerous honors, and was elected asThe step-scan measurements are performed under the master mode of the spectrometer (Thermo Nicolet, NEXUS 870), in which the timing trigger is initiated by the spectrometer. Figure 3 CHEMICAL SOCIETY Fig. 5. Schematic of the White cell. The first and second IR beam paths and the first and second UV photolysis beam paths of the multiply reflected light are shown. Circular dots indicate images of the IR beam at each reflection.