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Title: Radical Thermometers, Thermochemistry, and Photoelectron Spectra: A Photoelectron Photoion Coincidence Spectroscopy Study of the Methyl Peroxy Radical

Abstract

In this study, we investigated the simplest alkylperoxy radical, CH3OO, formed by reacting photolytically generated CH3 radicals with O2, using the new combustion reactions followed by photoelectron photoion coincidence (CRF-PEPICO) apparatus at the Swiss Light Source. Modeling the experimental photoion mass-selected threshold photoelectron spectrum using Franck–Condon simulations including transitions to triplet and singlet cationic states yielded the adiabatic ionization energy of 10.265 ± 0.025 eV. Dissociative photoionization of CH3OO generates the CH3+ fragment ion at the appearance energy of 11.164 ± 0.010 eV. Combining these two values with ΔfH0K°(CH3) yields ΔfH0K°(CH3OO) = 22.06 ± 0.97 kJ mol–1, reducing the uncertainty of the previously determined value by a factor of 5. Lastly, statistical simulation of the CH3OO breakdown diagram provides a molecular thermometer of the free radical’s internal temperature, which we measured to be 330 ± 30 K.

Authors:
 [1];  [2];  [1]; ORCiD logo [3]; ORCiD logo [3];  [3];  [4]; ORCiD logo [1]
  1. Univ. of the Pacific, Stockton, CA (United States)
  2. Univ. of Nevada, Reno, NV (United States)
  3. Paul Scherrer Institute, Villigen PSI (Switzerland)
  4. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1485829
Report Number(s):
SAND-2018-13191J
Journal ID: ISSN 1948-7185; 670054
Grant/Contract Number:  
AC04-94AL85000; NA0003525
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry Letters
Additional Journal Information:
Journal Volume: 9; Journal Issue: 3; Journal ID: ISSN 1948-7185
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Voronova, Krisztina, Ervin, Kent M., Torma, Krisztián G., Hemberger, Patrick, Bodi, Andras, Gerber, Thomas, Osborn, David L., and Sztáray, Bálint. Radical Thermometers, Thermochemistry, and Photoelectron Spectra: A Photoelectron Photoion Coincidence Spectroscopy Study of the Methyl Peroxy Radical. United States: N. p., 2017. Web. https://doi.org/10.1021/acs.jpclett.7b03145.
Voronova, Krisztina, Ervin, Kent M., Torma, Krisztián G., Hemberger, Patrick, Bodi, Andras, Gerber, Thomas, Osborn, David L., & Sztáray, Bálint. Radical Thermometers, Thermochemistry, and Photoelectron Spectra: A Photoelectron Photoion Coincidence Spectroscopy Study of the Methyl Peroxy Radical. United States. https://doi.org/10.1021/acs.jpclett.7b03145
Voronova, Krisztina, Ervin, Kent M., Torma, Krisztián G., Hemberger, Patrick, Bodi, Andras, Gerber, Thomas, Osborn, David L., and Sztáray, Bálint. Sun . "Radical Thermometers, Thermochemistry, and Photoelectron Spectra: A Photoelectron Photoion Coincidence Spectroscopy Study of the Methyl Peroxy Radical". United States. https://doi.org/10.1021/acs.jpclett.7b03145. https://www.osti.gov/servlets/purl/1485829.
@article{osti_1485829,
title = {Radical Thermometers, Thermochemistry, and Photoelectron Spectra: A Photoelectron Photoion Coincidence Spectroscopy Study of the Methyl Peroxy Radical},
author = {Voronova, Krisztina and Ervin, Kent M. and Torma, Krisztián G. and Hemberger, Patrick and Bodi, Andras and Gerber, Thomas and Osborn, David L. and Sztáray, Bálint},
abstractNote = {In this study, we investigated the simplest alkylperoxy radical, CH3OO, formed by reacting photolytically generated CH3 radicals with O2, using the new combustion reactions followed by photoelectron photoion coincidence (CRF-PEPICO) apparatus at the Swiss Light Source. Modeling the experimental photoion mass-selected threshold photoelectron spectrum using Franck–Condon simulations including transitions to triplet and singlet cationic states yielded the adiabatic ionization energy of 10.265 ± 0.025 eV. Dissociative photoionization of CH3OO generates the CH3+ fragment ion at the appearance energy of 11.164 ± 0.010 eV. Combining these two values with ΔfH0K°(CH3) yields ΔfH0K°(CH3OO) = 22.06 ± 0.97 kJ mol–1, reducing the uncertainty of the previously determined value by a factor of 5. Lastly, statistical simulation of the CH3OO breakdown diagram provides a molecular thermometer of the free radical’s internal temperature, which we measured to be 330 ± 30 K.},
doi = {10.1021/acs.jpclett.7b03145},
journal = {Journal of Physical Chemistry Letters},
number = 3,
volume = 9,
place = {United States},
year = {2017},
month = {12}
}

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Cited by: 11 works
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Figures / Tables:

Figure 1. Figure 1.: CH3+ and CH3OO+ kinetic traces in the presence of oxygen, integrated over the 10.24-11.31 eV photon energy range.

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