科研之友
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摘要
A method for studying the reactions of surface alkoxy radicals with O-2 at temperatures of 230 to 300 K is described. Alkoxy radicals were generated directly in the cavity of an EPR spectrometer. Surface organic radicals, prepared from paraffin wax ((CH3)(2)(CH2) (n) , n = 16-20), were applied to Aerosil particles from a solution in heptane. The Aerosil sample was placed in the cavity of the EPR spectrometer in a cylindrical cup with a central hole for pumping out gases and exposed to H atoms. In this way, it is possible observe a steady increase in the EPR signal from the surface radicals. To measure the rate constant at tropospheric temperatures, the reaction tube was placed in a Teflon jacket, through which cool nitrogen vapor was pumped. The temperature in the reactor was varied from 230 to 300 K. The recorded EPR spectra belong to the (RO) (s) radical. After obtaining a stable EPR signal from the surface radicals, treatment with H atoms was stopped, additional flow of O-2 was introduced ([O-2] = 10(14)-10(16) cm(-3)), and the reaction of O-2 with the surface organic radicals was studied by monitoring the EPR signal decay. The temperature dependence of the rate constant for the (RO) (s) + O-2 -> HO2 + ketone was obtained within T = 230-300 K. The extrapolation of the data to real tropospheric conditions ([O-2] = 10(18) cm(-3)) was performed.
- 出版日期2012-7
