D kinetic isotope effects measurement in the reactions of ch4 with o(1d) using cavity ring-down spectroscopy
Chen, TzuLing
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https://hdl.handle.net/2142/107627
Description
Title
D kinetic isotope effects measurement in the reactions of ch4 with o(1d) using cavity ring-down spectroscopy
Author(s)
Chen, TzuLing
Contributor(s)
Okumura, Mitchio
Ober, Douglas
Issue Date
2020-06-26
Keyword(s)
Dynamics and kinetics
Abstract
As a long-lived greenhouse gas, methane plays a major role in the chemistry of the Earth's atmosphere. Most atmospheric methane is removed by oxidations by OH (84\%) and O($^1$D) (8\%). The study of kinetic isotope effects (KIEs) on the reaction rate constants involving the transfer between hydrogen atoms is of importance but challenging experimentally because they are quite small.
In this work, the $^D$KIE for the singly substituted methane (CH$_3$D and CH$_4$) with O($^1$D) radicals have been measured using frequency-stabilized cavity ring down spectroscopy (FS-CRDS), where the isotopic composition is determined based on a dual near-infrared DFB laser system. The high sensitivity of the FS-CRDS system, with a detection limit of 6.0$\times$10$^{-12}$~cm$^{-1}$, enables the KIE to be measured with low depletion to minimize possible secondary effects.
In this experiment, the O($^1$D) radicals are produced by the 193~nm photolysis of N$_2$O. The preliminary result of $^D$KIE is 1.052(39).
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