In the air we breathe, invisible chemical events are constantly unfolding. One of them is the birth and instant death of a particle with the formula H₂COO. Known as an 'intermediate,' it appears for a split second when ozone molecules collide with organic compounds, then immediately shatters into simpler fragments.
The scientists built a computer model that replicates the behavior of every atom in this particle. The model showed that the particle can decay in three ways: into carbon dioxide and hydrogen, into water and carbon monoxide, or into two fragments — HCO and OH. For each pathway, the authors calculated how energy is distributed among the fragments — how much goes into their separation, how much into rotation, and how much into internal vibrations of the bonds.
The most intriguing result concerns the pathway that yields carbon dioxide and hydrogen. This pathway splits into two: the particle can break apart directly, or it can first momentarily transform into formic acid and only then decompose. Which route the decay takes determines whether the hydrogen molecule will vibrate (i.e., carry excess vibrational energy) or remain calm.
This matters for understanding atmospheric chemistry: such short-lived particles influence how quickly the air cleans itself of pollutants. If we want to accurately predict the composition of air over a city or a forest, we need to know exactly what these invisible couriers decay into and with what energy their fragments fly apart.
The H₂COO particle lives for less than one billionth of a second, yet in that time it manages to choose one of several decay pathways, as if it had multiple doors and dives through one of them.