Direct measurements of DOCO isomers in the kinetics of OD+CO

TL;DR

This study employs time-resolved frequency comb spectroscopy to directly measure and analyze the transient DOCO isomers during the OD+CO reaction, providing detailed mechanistic insights into this fundamental chemical process.

Contribution

It introduces a novel application of frequency comb spectroscopy to directly observe and quantify DOCO isomers, advancing understanding of reaction dynamics involving hydroxyl radicals.

Findings

Quantified the concentrations of DOCO isomers during the reaction.

Determined the pressure and collision partner dependence of reaction pathways.

Provided detailed kinetic data on isomerization and dissociation processes.

Abstract

Quantitative and mechanistically-detailed kinetics of the reaction of hydroxyl radical (OH) with carbon monoxide (CO) have been a longstanding goal of contemporary chemical kinetics. This fundamental prototype reaction plays an important role in atmospheric and combustion chemistry, motivating studies for accurate determination of the reaction rate coefficient and its pressure and temperature dependence at thermal reaction conditions. This intricate dependence can be traced directly to details of the underlying dynamics (formation, isomerization, and dissociation) involving the reactive intermediates cis- and trans-HOCO, which can only be observed transiently. Using time-resolved frequency comb spectroscopy, comprehensive mechanistic elucidation of the kinetics of the isotopic analogue deuteroxyl radical (OD) with CO has been realized. By monitoring the concentrations of reactants, intermediates, and products in real-time, the branching and isomerization kinetics and absolute yields of all species in the OD+CO reaction are quantified as a function of pressure and collision partner.