Scientists solve mystery of highly reactive oxygen
Researchers have unraveled a decades-old puzzle in chemistry by explaining how oxygen becomes highly reactive in certain conditions. The breakthrough, detailed in a recent study, reveals a new mechanism involving atomic oxygen reactions. This discovery could reshape understandings of atmospheric processes and combustion.
For over 50 years, chemists have been baffled by the behavior of highly reactive oxygen, particularly in the form known as singlet oxygen, which plays a crucial role in reactions from photosynthesis to pollution. A team led by David Osborn at Sandia National Laboratories in the United States has finally cracked the mystery through advanced experimental techniques.
The study, published in the journal Science on October 10, 2024, focused on the reaction between oxygen atoms and molecular oxygen. Using a method called velocity map imaging, the researchers observed the fleeting intermediates in the reaction O + O2 → O3, but with a twist: they identified a pathway leading to the formation of highly reactive triplet-state oxygen products.
"This reaction has been a black box for so long," Osborn said in an interview with New Scientist. "We now see exactly how energy is distributed, explaining why oxygen can suddenly become so aggressive in breaking bonds."
The background to this puzzle dates back to the 1970s, when early experiments showed inconsistencies in oxygen reactivity rates under different pressures and temperatures. Previous models assumed simple energy transfer, but they failed to account for quantum effects that allow oxygen to access forbidden electronic states.
This new insight confirms details from multiple computational simulations done in the 2010s, resolving discrepancies where lab data clashed with theory—for instance, earlier reports suggested reaction rates 10 times higher than predicted, while this work aligns them precisely.
Implications extend beyond pure chemistry. In the atmosphere, this mechanism could influence ozone depletion and the formation of smog, affecting climate models. In industry, better predictions of oxygen's reactivity might improve engine designs and reduce emissions from combustion processes.
The research was conducted using state-of-the-art facilities at Sandia's Combustion Research Facility, highlighting the role of national labs in fundamental science. While the team emphasizes the need for further validation in complex environments, this solves a core enigma that has eluded scientists for generations.