
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.
Technical Details
It is difficult to probe a complex chemical system holistically. Although a “perfect” experimental approach doesn’t exist for all systems, several criteria would clearly be advantageous. 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 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 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 pathways from reactants, through intermediates, and to multiple simultaneous products. Resulting high-fidelity, multiplexed data sets provide important constraints to theoretical models of chemical reactions, which combine with experiments to advance foundational knowledge of chemistry.
Key Contributions
- Isomeric-resolved identification of reactive intermediates
- Elucidation of detailed reaction pathways in combination with theoretial chemistry
Partners
- Marsha I. Lester, University of Pennsylvania
- Mitchio Okumura, California Institute of Technology
- Carl Percival, Jet Propulsion Laboratory
- Andrew Orr-Ewing, University of Bristol
- Dudley Shallcross, University of Bristol
PIs: Nils Hansen, Craig A. Taatjes, David L. Osborn, and Leonid Sheps

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