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Title: Critical Assessment of Photoionization Efficiency Measurements for Characterization of Soot-Precursor Species

Abstract

We present a critical evaluation of photoionization efficiency (PIE) measurements coupled with aerosol mass spectrometry for the identification of condensed soot-precursor species extracted from a premixed atmospheric-pressure ethylene/oxygen/nitrogen flame. Definitive identification of isomers by any means is complicated by the large number of potential isomers at masses likely to comprise particles at flame temperatures. This problem is compounded using PIE measurements by the similarity in ionization energies and PIE-curve shapes among many of these isomers. Nevertheless, PIE analysis can provide important chemical information. For example, our PIE curves show that neither pyrene nor fluoranthene alone can describe the signal from C 16H 10 isomers and that coronene alone cannot describe the PIE signal from C 24H 12 species. A linear combination of the reference PIE curves for pyrene and fluoranthene yields good agreement with flame-PIE curves measured at 202 u, which is consistent with pyrene and fluoranthene being the two major C 16H 10 isomers in the flame samples, but does not provide definite proof. The suggested ratio between fluoranthene and pyrene depends on the sampling conditions. We calculated the values of the adiabatic-ionization energy (AIE) of 24 C 16H 10 isomers. Despite the small number of isomers considered, themore » calculations show that the differences in AIEs between several of the isomers can be smaller than the average thermal energy at room temperature. The calculations also show that PIE analysis can sometimes be used to separate hydrocarbon species into those that contain mainly aromatic rings and those that contain significant aliphatic content for species sizes investigated in this study. Our calculations suggest an inverse relationship between AIE and the number of aromatic rings. We have demonstrated that further characterization of precursors can be facilitated by measurements that test species volatility.« less

Authors:
ORCiD logo [1]; ORCiD logo [1];  [2];  [1];  [1];  [3];  [3]; ORCiD logo [2];  [1]
  1. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
  2. Univ. of Michigan, Ann Arbor, MI (United States)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-CA), Livermore, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1365807
Alternate Identifier(s):
OSTI ID: 1456974
Report Number(s):
SAND-2017-5882J
Journal ID: ISSN 1089-5639; 653852
Grant/Contract Number:  
AC04-94AL85000; AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory
Additional Journal Information:
Journal Volume: 121; Journal Issue: 23; Journal ID: ISSN 1089-5639
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Johansson, K. Olof, Z?dor, Judit, Elvati, Paolo, Campbell, Matthew F., Schrader, Paul E., Richards-Henderson, Nicole K., Wilson, Kevin R., Violi, Angela, and Michelsen, Hope A. Critical Assessment of Photoionization Efficiency Measurements for Characterization of Soot-Precursor Species. United States: N. p., 2017. Web. doi:10.1021/acs.jpca.7b02992.
Johansson, K. Olof, Z?dor, Judit, Elvati, Paolo, Campbell, Matthew F., Schrader, Paul E., Richards-Henderson, Nicole K., Wilson, Kevin R., Violi, Angela, & Michelsen, Hope A. Critical Assessment of Photoionization Efficiency Measurements for Characterization of Soot-Precursor Species. United States. doi:10.1021/acs.jpca.7b02992.
Johansson, K. Olof, Z?dor, Judit, Elvati, Paolo, Campbell, Matthew F., Schrader, Paul E., Richards-Henderson, Nicole K., Wilson, Kevin R., Violi, Angela, and Michelsen, Hope A. Thu . "Critical Assessment of Photoionization Efficiency Measurements for Characterization of Soot-Precursor Species". United States. doi:10.1021/acs.jpca.7b02992. https://www.osti.gov/servlets/purl/1365807.
@article{osti_1365807,
title = {Critical Assessment of Photoionization Efficiency Measurements for Characterization of Soot-Precursor Species},
author = {Johansson, K. Olof and Z?dor, Judit and Elvati, Paolo and Campbell, Matthew F. and Schrader, Paul E. and Richards-Henderson, Nicole K. and Wilson, Kevin R. and Violi, Angela and Michelsen, Hope A.},
abstractNote = {We present a critical evaluation of photoionization efficiency (PIE) measurements coupled with aerosol mass spectrometry for the identification of condensed soot-precursor species extracted from a premixed atmospheric-pressure ethylene/oxygen/nitrogen flame. Definitive identification of isomers by any means is complicated by the large number of potential isomers at masses likely to comprise particles at flame temperatures. This problem is compounded using PIE measurements by the similarity in ionization energies and PIE-curve shapes among many of these isomers. Nevertheless, PIE analysis can provide important chemical information. For example, our PIE curves show that neither pyrene nor fluoranthene alone can describe the signal from C16H10 isomers and that coronene alone cannot describe the PIE signal from C24H12 species. A linear combination of the reference PIE curves for pyrene and fluoranthene yields good agreement with flame-PIE curves measured at 202 u, which is consistent with pyrene and fluoranthene being the two major C16H10 isomers in the flame samples, but does not provide definite proof. The suggested ratio between fluoranthene and pyrene depends on the sampling conditions. We calculated the values of the adiabatic-ionization energy (AIE) of 24 C16H10 isomers. Despite the small number of isomers considered, the calculations show that the differences in AIEs between several of the isomers can be smaller than the average thermal energy at room temperature. The calculations also show that PIE analysis can sometimes be used to separate hydrocarbon species into those that contain mainly aromatic rings and those that contain significant aliphatic content for species sizes investigated in this study. Our calculations suggest an inverse relationship between AIE and the number of aromatic rings. We have demonstrated that further characterization of precursors can be facilitated by measurements that test species volatility.},
doi = {10.1021/acs.jpca.7b02992},
journal = {Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory},
number = 23,
volume = 121,
place = {United States},
year = {Thu May 18 00:00:00 EDT 2017},
month = {Thu May 18 00:00:00 EDT 2017}
}

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