This work continues and further develops a highly successful collaboration among several institutions in the US and Brazil to investigate the interactions of low-energy electrons with polyatomic molecules, and in particular with biofuels and other biological molecules. The collaboration includes scientists from California State University, Fullerton, the California Institute of Technology, the State University of Campinas. It involves both experimental and theoretical groups who have come together to work jointly on problems where they have overlapping interests and complementary expertise. Major focuses in future work will be electron-impact excitation of polyatomic molecules and dissociative electron attachment to polyatomics. Calculations and measurements of electron-impact excitation processes in polyatomics are challenging, and results are scarce despite the need for such data in understanding reactive plasmas and discharges. To build expertise in this area, measurements and calculations are carried out for two prototypical molecules, ethylene and furan, both of which have low-lying triplet states well isolated from other thresholds. Following that, measurements and calculations of electron-impact excitation cross sections for methanol and ethanol will be done. Electron-impact excitation of these prototypical and ubiquitous alcohols is of fundamental interest and also has high technological relevance: dissociative excitation and ionization are key processes in spark ignition of alcohol fuels, and rate data are needed for modeling and optimizing the ignition process. Collaborators in Brazil affiliated with the Bioethanol Science and Technology Center in Campinas are initiating studies of spark ignition that will involve both laboratory measurements and numerical modeling, and those studies will make direct use of the electron-impact excitation cross sections that will be measured and calculated as part of this project.
The broader impacts are that electron-molecule collisions at low energy present many features of fundamental interest and pose a great challenge to both experimental and computational methods, but they also have wide technological significance, being relevant to the physics of plasmas and discharges, the upper atmosphere, and circumstellar and interstellar media. In the specific case of methanol and ethanol, accurate cross-section data for the major collision processes, including elastic scattering, excitation, and ionization, are needed for numerical modeling and optimization of discharges used to ignite alcohols used as fuels. Such modeling may lead to improved spark-plug designs that produce more complete combustion and thus higher fuel efficiency. Moreover, an understanding of electron driven excitation and dissociation in the alcohols may give insights into the same processes in related biomolecules, including sugars. A central component of the project is providing opportunities for young scientists to gain experience doing science in an international context, with US students making extended visits to do research in Brazil and vice versa. This project is co-funded with the Americas Program of the Office of International Science and Engineering.
We continued our work in differential electron spectroscopy of polyatomic targets and sent 4 students to Brazil (Brent Yates, Ling Hong, Josh Tanner and Danny Orton) to the laboratory of Dr. Cristina Lopes at University of Juiz de Fora, in the state of Minas Gerais. We published 10 papers and involved many undergraduate and masters students including minorities, viz.: Rehab Albaridy (now a university teacher in Riyadh, Saudi Arabia), Gabriela Serna (now doing her masters at CSUF), Alex Gauf (doing a masters in Maths at CSUF), Josh Tanner (applying for PhD schools), Amos Jo (coming back to do a masters at CSUF), Todd Walls (High School Teacher, did his masters at CSUF as a local HS Teacher), Bahar Ajdari (doing PhD at Oakland University), Brent Yates (PhD at UC Riverside), Ling Hong (Phd a UC Riverside), Kevin Ralphs (PhD at Purdue U, Indiana), Cristian Navarro (taking a year off after his BSc), Colin Campbell (PhD at Australian U., Canberra), G. Balch (Masters in Engineering, CSUF), Nick Meyer (BSc Physics at Caltech), Adrienne Chang (BSc UC Santa Barbara), Kenneth Varela (PhD Penn. State U). We gave several colloquia and poster presentations (15 altogether, at DAMOP, GEC and ICPEAC). I had a postdoc, Dr. Leigh Hargreaves, from Flinders University in Adelaide, Australia. He has been here 3.5 years and just became a tenure track faculty in our physics department! He has trained on the equipment as well as mentoring students and teaching courses in physics. He has been a very popular teacher. He gave invited and contributed talks at conferences. We published imprtant papers on the excitation of water at low energies, and got good agreement with our collaborators at Caltech on several of these papers. We did the excitation of Furan with the Brazil group. Here the agreement was less satisfactory. Altogether collaboration with Brazil and Caltech has been very congenial and a happy one. The exchange of ideas has flowed freely and enjoyably. I got a visit from Dr. Kamil Fedus from Nicholas Copernicus U., in Torun, Poland as a Fulbright Scholar. With him we worked on elastic scattering from isobutanol, pentane and methyl chloride. Presently we are sitting on 4 papers - the first on excitation of methanol (which is considered important)- and the bottleneck seems to be theory from Caltech which is finding the experimental data difficult to model. Overall this has been a productive area of research and basically we are stretched for time to do many things, as the apparatus is working very well. Presently a versatile well-tested spectrometer that has a lare incident electron energy range. We are developing in tandem, an electron time-of-flight spectrometer which is almost near completion, and will be very useful as a low energy instrument as well as a calibration standard for other scattering experiments.
