Balint Sztaray, a professor of Chemistry at University of the Pacific

Balint Sztaray, a professor of Chemistry at University of the Pacific

Over the past two summers and a sabbatical semester in 2013, University of the Pacific (UOP) chemistry professor Balint Sztaray and his research group have been working with the CRF’s David Osborn on a project to improve the selectivity of the current multiplexed gas-phase chemical kinetics instrument. Specifically, the two researchers are focusing on developing a new instrument that combines Balint’s method of photoelectron-photoion coincidence spectroscopy with David’s multiplexed photoionization mass spectrometry (PIMS).

DOE has been a partner in this effort, providing funding to Balint through its Visiting Faculty Program (VFP). Part of the larger Workforce Development for Teachers and Scientists (WDTS) program run by DOE’s Office of Science, VFP is designed to increase research competitiveness by allowing a college or university faculty member and up to two students to conduct 10 weeks of collaborative research with national laboratory staff.

Kyle Covert, a Ph.D. student at University of the Pacific.

Kyle Covert, a Ph.D. student at University of the Pacific.

Once again a VFP award recipient, Balint will be back at the CRF this summer, along with UOP Ph.D. student Kyle Covert, to work with David on bringing their concept closer to reality. Their work to date, which included a trip to Switzerland to run experiments on a unique endstation at the Swiss Light Source (SLS), was described in detail in a proof-of-concept paper published in the prestigious Journal of Physical Chemistry Letters.

As discussed, PIMS—which applies tunable synchrotron light to enable isomer separation based on unique photoionization spectra—is a powerful method for time- and space-resolved chemical analysis of reactants, intermediates, and products. However, when three or more isomers are present, identification by photoionization spectra alone can be challenging.

Through experiments at SLS, the researchers showed that imaging photoelectron-photoion coincidence (iPEPICO) spectroscopy—which measures photoelectron spectra corresponding to each cation mass-to-charge (m/z) ratio—provides a more detailed spectral fingerprint than does photoionization spectroscopy. Figure 1 shows the additional information available from the iPEPICO approach.

Figure 1. This graph highlights the rich information offered by the proposed iPEPICO method. It shows the threshold photoelectron spectrum (TPES) of a butadiene/2-butyne mixture (red curve), together with the individual TPES spectra (blue and green curves). Also provided are the photoionization spectra of the mixture (black curve) and of butadiene (dotted line).

Figure 1. This graph highlights the rich information offered by the proposed iPEPICO method. It shows the threshold photoelectron spectrum (TPES) of a butadiene/2-butyne mixture (red curve), together with the individual TPES spectra (blue and green curves). Also provided are the photoionization spectra of the mixture (black curve) and of butadiene (dotted line).

“This summer, David and I will be building on these preliminary results and, with Kyle’s assistance, designing a testbed experiment that will fit into the existing iPEPICO endstation at the VUV [vacuum ultraviolet] beamline of the SLS,” said Balint. The team plans to travel to the SLS in the fall to test a prototype design, and then design and build a new apparatus for the chemical dynamics beamline of the Advanced Light Source at Lawrence Berkeley National Laboratory, the planned successor of the current very successful multiplex PIMS instrument.

“It’s great to have Balint back at the CRF to continue this project,” said David. “And we appreciate DOE’s support of Balint and Kyle through the Visiting Faculty Program. This collaborative work will bring us closer to identifying all the species present in combustion reactions so that the CRF can continue to contribute to cleaner and more efficient engines.”

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