Researchers at Lawrence Berkeley National Laboratory, or Berkeley Lab, the University of Hawaii at Manoa and Florida International University released research May 21 confirming that free radicals can react and form benzene under conditions that are prevalent in interstellar space.
For nearly a decade, Musahid Ahmed, senior scientist of chemistry at Berkeley Lab, Ralf Kaiser, professor of chemistry at the University of Hawaii at Manoa and Alexander Mebel, professor of chemistry and biochemistry at Florida International University, have worked on a series of models and experiments to study how soot forms, according to Ahmed.
Producing more than 30 papers in the course of more than 10 years, their study was published in the journal Science Advances, further exploring this mechanism.
“The reason our paper made it to this high profile journal is because what we predicted is what we saw,” Ahmed said. “That gives you some faith that the hypothesis we had is correct. This becomes important, because if you can model something that is correct, then you extrapolate that to temperatures and pressures, which we can’t do with an experiment.”
The experiments conducted by the researchers took place in 2019. Kaiser said through the use of the Advanced Light Source at Berkeley Lab, the researchers were able to detect not only benzene but also three other higher-energy structural isomers that were formed.
Polycyclic aromatic hydrocarbons, or PAHs, can be detrimental to human health and can act as carcinogens, according to Kaiser. Naturally appearing in outer space, PAHs can also be produced when car engines burn fossil fuel; the chemical reaction responsible for their creation occurs in both scenarios.
“In space, (aromatic compounds) are actually supportive and critical to understanding the carbon balance,” Kaiser said. “On Earth, PAHs are really unwanted byproducts that we have to eliminate, and we have to understand how they are formed before we can eliminate them.”
While others have attempted to conduct this experiment in decades past, this group of researchers is the first to achieve success. Kaiser attributed previous shortcomings to loosely defined experimental conditions and analytical tools that could not distinguish between multiple structural isomers.
Although the research may not produce direct or immediate applications, it advances the subject and contributes to a larger, fundamental body of knowledge, according to Ahmed.
“It is not like this will give me a better car engine tomorrow or it will explain to me how some molecules form, but it goes into a body of knowledge that allows you to think about how origins of the universe took place, or how you will design the car engine,” Ahmed said. “It is a small part of a bigger picture.”