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Chemistry Research on Cover of Journal

Quantum chemical effects in diesel ignition described by Dr. Zhang and Professor Dibble

Chemists and engineers are trying to understand how the chemical reactions of very short-lived molecules influences the ignition of diesel fuel. An important class of reactions is the isomerization of peroxy radicals (ROO), which leads to propagating and accelerating the ignition process. Because these molecules are short-lived and are formed in small concentrations, they are hard to detect. This means that theoretical calculations of their properties are usually needed to provide a complete understanding of their reactivity. The new study by Dr. Zhang and Professor Dibble examines how the quantum mechanical nature of the molecules changes their reactivity.

The problem is how a molecule without enough energy to isomerize can still undergo this reaction. The rigorous calculation of tunneling effects carried out by Dr. Zhang showed that tunneling can dominate the classical rate constant even at temperatures relevant to diesel ignition. In addition, less rigorous methods of computing tunneling do not always capture the full extent of tunneling, which can lead to significant underestimating rate constants for reaction. The significance of this research was recognized by making it the cover article for the journal which published it: Physical Chemistry Chemical Physics.