A 193-nm-laser photofragmentation time-of-flight mass spectrometric study of dimethylsulfoxide
- Ames Laboratory, USDOE, and Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States)
- Department of Chemistry, Iowa State University, Ames, Iowa 50011 (United States)
The photodissociation of dimethylsulfoxide [(CH{sub 3}){sub 2}SO] at 193.3 nm has been investigated using the molecular beam time-of-flight (TOF) mass spectrometric technique. In addition to CH{sub 3} and SO, CH{sub 3}SO is also observed as a stable primary product, indicating that CH{sub 3}SO+CH{sub 3} is an important product channel for the 193.3 nm photodissociation of (CH{sub 3}){sub 2}SO. The analysis of the TOF data provides evidence that SO is formed via a stepwise mechanism: (CH{sub 3}){sub 2}SO+h{nu} (193.3 nm){r_arrow}CH{sub 3}SO+CH{sub 3}{r_arrow}2CH{sub 3}+SO. The analysis also indicates that {approx}53{percent} of the primary CH{sub 3}SO radicals undergo further dissociation to produce CH{sub 3}+SO, yielding a quantum yield of {approx}1.53 for CH{sub 3}. Within the sensitivity of our experiment, the product channel of CH{sub 3}SCH{sub 3}+O is not found. The angular distribution for the formation of CH{sub 3}SO+CH{sub 3} is found to be isotropic, an observation consistent with a predissociation mechanism, in which the dissociation of photoexcited (CH{sub 3}){sub 2}SO is slow compared to its rotational period. The energetics for selected dissociation reactions of (CH{sub 3}){sub 2}SO have also been investigated by {ital ab initio} calculations at the G2(MP2) level of theory. The experimental dissociation energy at 0 K (53{plus_minus}2 kcal/mol) for the CH{sub 3}{endash}SOCH{sub 3} bond obtained here is in excellent agreement with the theoretical prediction of 52.6 kcal/mol. {copyright} {ital 1997 American Institute of Physics.}
- Research Organization:
- Ames National Laboratory
- DOE Contract Number:
- W-7405-ENG-82
- OSTI ID:
- 435117
- Journal Information:
- Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 1 Vol. 106; ISSN 0021-9606; ISSN JCPSA6
- Country of Publication:
- United States
- Language:
- English
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