Title

Highly Accurate Dissociation Dynamics of Methyl Hydroperoxide (CH3OOH) by TPEPICO

Poster Number

6

Lead Author Affiliation

Chemistry

Introduction

Methyl hydroperoxide (MHP) is an important gas phase molecule that contributes to oxidation and radical propagation in combustion chemistry. MHP is also the simplest organic hydroperoxide (ROOH) that is difficult to synthesize and study due to its explosive properties. Dissociation dynamics of this molecule have been studied but, most of the research is focused on cleaving the O-O bond. Beyond that, a few studies contain qualitative data on the dissociation fragments.

Purpose

Much is not understood about the fragmentation pathway or thermodynamics of MHP. MHP can undergo unimolecular dissociation to form a QOOH ion, one of the most sought after and important species in combustion chemistry. From there, the thermochemistry of the QOOH radical can be obtained.

Method

In this experiment, MHP is fragmented by way of photodissociation and various energy selected photoions are measured very accurately using Threshold Photoelectron Photoion Coincidence spectroscopy (TPEPICO). Tunable vacuum ultraviolet light from the Swiss Light Source synchrotron in Switzerland is used to photoionize and dissociate molecules into photoions. Threshold electrons (zero kinetic energy) are detected in coincidence with their photoions by imaging detectors. This allows for true coincidence measurements yielding highly accurate energetics of the ions.

Results

This work is the first time highly accurate energy selected dissociation has been performed with MHP. The breakdown diagram for MHP shows the fractional abundance of photoions depending on the amount of energy put into the system. Due to the nature of selecting only zero kinetic electrons in TPEPICO detection, the energy corresponds to the internal energy of the ions. From this, thermodynamic data can be obtained for the analyte such as 0K heats of formation and adiabatic ionization energy. Advanced modeling and ab intio calculations were performed to find said values and gain an understanding of the fragmentation pathways.

Significance

Understanding the fragmentation pathway of MHP leads insight into combustion reactions of this molecule and the products it may form. The thermodynamics are equally important giving us a view on the stability, and energy that can be released by MHP. This all contributes in understanding the complex radical chain propagation of lowtemperature combustion chemistry.

Location

DeRosa University Center, Stockton campus, University of the Pacific

Format

Poster Presentation

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Apr 25th, 2:00 PM Apr 25th, 4:00 PM

Highly Accurate Dissociation Dynamics of Methyl Hydroperoxide (CH3OOH) by TPEPICO

DeRosa University Center, Stockton campus, University of the Pacific

Methyl hydroperoxide (MHP) is an important gas phase molecule that contributes to oxidation and radical propagation in combustion chemistry. MHP is also the simplest organic hydroperoxide (ROOH) that is difficult to synthesize and study due to its explosive properties. Dissociation dynamics of this molecule have been studied but, most of the research is focused on cleaving the O-O bond. Beyond that, a few studies contain qualitative data on the dissociation fragments.