Radical Thermometers, Thermochemistry, and Photoelectron Spectra: A Photoelectron Photoion Coincidence Spectroscopy Study of the Methyl Peroxy Radical
Journal Article
·
· Journal of Physical Chemistry Letters
- Univ. of the Pacific, Stockton, CA (United States)
- Univ. of Nevada, Reno, NV (United States)
- Paul Scherrer Institute, Villigen PSI (Switzerland)
- Sandia National Lab. (SNL-CA), Livermore, CA (United States)
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.
- Research Organization:
- Sandia National Laboratories (SNL-CA), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- Grant/Contract Number:
- AC04-94AL85000; NA0003525
- OSTI ID:
- 1485829
- Report Number(s):
- SAND--2018-13191J; 670054
- Journal Information:
- Journal of Physical Chemistry Letters, Journal Name: Journal of Physical Chemistry Letters Journal Issue: 3 Vol. 9; ISSN 1948-7185
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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