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[B-4.2 Kinetic Measurement on Gas-Phase Reactions Related to Global Warming]

[Contact Person]

Nobuaki Washida
Director, Atmosheric Environmental Division
National Institute for Environmental Studies
Environmental Agency
16-2 Onogawa, Tsukuba, Ibaraki 305 Japan
Phone +81-298-51-6111(Ext.350), Fax +81-298-51-4732

[Total Budget for FY1990-1992]

28,910,000 Yen

[Abstract]

　In this research project, the intensity of the ionizing light of photoionization mass spectrometer was greatly enhanced, and hence the detection sensitibity for radicals was increased by a factor of about 50. The CH₃O₂ and HO₂ radicals were able to be detected directly as the parent ions at m/e = 47 and 33, respectively. Reactions of CH₃O₂ and HO₂ with NO were studied by time-resolved measurements of the radical ion signals. The following rate constants were obtained at 298±5K:
　　 k(CH₃O₂+NO) = (11.2±1.4)10^-12cm³molecule^-1s^-1,
　　 k(HO₂+NO) = (6.3±2.1)10^-12cm³molecule^-1s^-1.
The value for k(CH₃O₂+NO) is 50% larger than that previouly reported.
　The HOCO radical, which has been inferred to be an intermediate of the reaction of OH + CO, was successfully detected by the photoionization mass spectrometry in gas phase. Unimolecular processes of the radical were investigated in gas phase for the first time by time-resolved measurements. The rate constant for thc reaction of HOCO with O₂ was determined, and appeared pressure-inderpendent.

[Key Words]

CH₃O₂, HOCO, HO₂, Photoionization mass spectrometry, Reaction rate constant