Photoionization Mass Spectrometry

The reactor tube and skimmer of one multiplexed photoionization mass spectrometer at the CRF, which is optimized for the study of low-pressure individual reactions and reaction sequences. Source: D. Osborn, Sandia National Laboratories.
Figure 1 The reactor tube and skimmer of one multiplexed photoionization mass spectrometer at the CRF, which is optimized for the study of low-pressure individual reactions and reaction sequences. Source: D. L. Osborn, Sandia National Laboratories

Technical Details

It is difficult to probe a complex chemical system holistically. Although a “perfect” experimental approach doesn’t exist for all systems, several goals are clear. An optimal technique would have the following characteristics:

  • Universal: probes all species regardless of their chemical nature
  • Selective: can identify and quantify different isomers in chemical reactions
  • Sensitive: can detect minute quantities of a chemical
  • Time-resolved: follows creation and consumption of each species in time
  • Multiplexed: probes all these aspects simultaneously, in a single experiment

The Combustion Research Facility has been a pioneer in developing multiplexed photoionization mass spectrometry, a technique that meets most or all these goals. We have applied this technique broadly in studies of flame chemistry, unexpected chemical intermediates (such as enols), chemistry on Saturn’s moon Titan, Criegee intermediates important in Earth’s atmosphere, combustion chain branching, chemical mechanisms at high pressures, and heterogeneous catalysis. These studies provide both broad and deep views of chemical reaction mechanisms by their ability to expose and quantify chemical pathways from reactants, through intermediates, and to multiple simultaneous products. The resulting high-fidelity, multiplexed experimental data sets constrain theoretical models of chemical reactions to advance foundational knowledge in chemistry.

custom-built multiplexed photoionization mass spectrometer

Figure 2 A custom-built multiplexed photoionization mass spectrometer for the study of chemical reactions at pressures up to 100 atm. Source: Sandia National Laboratories.

Key Contributions

  • Isomeric-resolved identification of reactive intermediates
  • Elucidation of detailed reaction pathways in combination with theoretical chemistry

Partners

  • Marsha I. Lester, University of Pennsylvania
  • Mitchio Okumura, California Institute of Technology
  • Carl Percival, Jet Propulsion Laboratory
  • Frank A.F. Winiberg, Jet Propulsion Laboratory
  • Andrew Orr-Ewing, University of Bristol
  • Dudley Shallcross, University of Bristol
  • Adam J. Trevitt, University of Wollongong
  • Stephen J. Klippenstein, Argonne National Laboratory
  • Rebecca L. Caravan, Argonne National Laboratory
  • Ahren W. Jasper, Argonne National Laboratory
  • Brandon Rotavera, University of Georgia
  • Arkke Eskola, University of Helsinki
  • Fabien Goulay, West Virginia University
  • Talitha M. Selby, University of Wisconsin-Milwaukee
  • Sebastien D. Le Picard, University of Rennes
  • Christopher Hansen, University of New South Wales
  • Hanna Reisler, University of Southern California
  • Coleman X. Kronawitter, University of California, Davis
  • Denisia M. Popolan-Vaida, University of Central Florida
  • John D. Savee, KLA

PIs: Nils Hansen, Craig A. Taatjes, David L. Osborn, and Leonid Sheps