CaltechTHESIS
  A Caltech Library Service

Laboratory studies of the self and cross reactions of atmospheric peroxy radicals

Citation

Noell, Aaron Craig (2010) Laboratory studies of the self and cross reactions of atmospheric peroxy radicals. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:01252010-225602127

Abstract

My studies focused on the self and cross reactions of peroxy radicals (RO2). These are important gas phase reactions in the atmosphere when concentrations of nitrogen oxides are low. Hydroperoxide products of these reactions can undergo further reaction to form aerosol precursors, making RO2 reactions critical to aerosol formation as well. The occurrence of multiple simultaneous reactions is frequently unavoidable when working with radical reactions. Self reactions of RO2 further complicate matters by producing another peroxy radical (HO2) through one of their product channels. Time resolved spectroscopic probes in the ultraviolet and near-infrared, specifically targeting each reactant, were used to measure the rate coefficients for the self and cross reactions of HO2 and ethyl peroxy radicals (C2H5O2). In addition the product branching fraction leading to HO2 was determined for the C2H5O2 self reaction with results very different from the literature. Further work on the self reaction branching fractions of methyl peroxy, ethyl peroxy, and propyl peroxy was done to try and resolve the discrepancy with the literature. A photoionization mass spectrometry technique was used to monitor all of the stable reaction products on the timescale of the reaction. The literature work had used end product studies after the reactions had completed to measure all of the stable products. Results from the photoionization studies appear to agree with the spectroscopic work for the C2H5O2 self reaction, indicating that additional secondary chemistry may have skewed the results in the literature. Aerosol nucleation observed in low temperature experiments on the HO2 self reaction was another area of work. Radical chemistry is the main driver of gas phase atmospheric cycles, but is not currently thought to be at the center of new particle formation. Radical-molecule complexes between HO2 and a number of species including methanol, water, and acetone could act as particle seeds at low temperature due to the stability of their hydrogen bonds. Most of the nucleation work described is on the HO2 - methanol complex, but all three were investigated. Lastly, the experimental calibrations and general procedures that went on throughout all this work are described.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Atmospheric Chemistry; Peroxy Radical; HO2; Ethyl Peroxy; C2H5O2; Photoinduced Nucleation
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Mixed availability, specified at file level
Research Advisor(s):
  • Okumura, Mitchio (advisor)
  • Sander, Stanley P. (co-advisor)
Thesis Committee:
  • Blake, Geoffrey A. (chair)
  • Marcus, Rudolph A.
  • Beauchamp, Jesse L.
Defense Date:18 November 2009
Author Email:anoell (AT) jpl.nasa.gov
Record Number:CaltechTHESIS:01252010-225602127
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:01252010-225602127
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5540
Collection:CaltechTHESIS
Deposited By: Aaron Noell
Deposited On:19 Mar 2010 17:06
Last Modified:26 Dec 2012 03:21

Thesis Files

[img]
Preview
PDF (Chapter 5 (Experimental)) - Final Version
See Usage Policy.

748Kb
[img]
Preview
PDF (Chapter 4 (Nucleation)) - Final Version
See Usage Policy.

1369Kb
[img]
Preview
PDF (Chapter 1 (Introduction)) - Final Version
See Usage Policy.

73Kb
[img]
Preview
PDF (Title page and table of contents) - Final Version
See Usage Policy.

56Kb
[img]
Preview
PDF (Chapter 3 (ALS RO2 branching ratio)) - Final Version
See Usage Policy.

5Mb
[img]
Preview
PDF (Chapter 2 (HO2 + C2H5O2)) - Final Version
See Usage Policy.

1844Kb
[img]
Preview
PDF (Full Thesis) - Final Version
See Usage Policy.

9Mb

Repository Staff Only: item control page