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

In this study, we investigated the simplest alkylperoxy radical, CH 3OO, formed by reacting photolytically generated CH 3 radicals with O 2, 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 CH 3OO generates the CH 3 + fragment ion at the appearance energy of 11.164 ± 0.010 eV. Combining these two values with Δ fH 0K°(CH 3) yields Δ fH 0K°(CH 3OO) = 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 CH 3OO 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:
Report Number(s):
SAND-2018-13191J
Journal ID: ISSN 1948-7185; 670054
Grant/Contract Number:
AC04-94AL85000; NA0003525
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
Research Org:
Sandia National Lab. (SNL-CA), Livermore, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1485829

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., Web. doi: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. doi: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. 2017. "Radical Thermometers, Thermochemistry, and Photoelectron Spectra: A Photoelectron Photoion Coincidence Spectroscopy Study of the Methyl Peroxy Radical". United States. doi: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}
}