Accelerated Hydrogen Exchange Reaction in a Dark Cavity: A Benchmark for Bridging the Gap Between Theory and Experiment

The gas-phase hydrogen exchange reaction (HER) is the most fundamental chemical process for benchmarking quantum reaction dynamics. In this Letter, we focus on controlling HER by means of strong light-matter coupling inside a resonant cavity, an approach often called polariton chemistry. In particular, we focus on the isotopic variation of HER involving collisions between molecular hydrogen H₂ and deuterium atom D, i.e., H₂+D→HD+H. We find that the asymmetry introduced by the different isotopes, despite being small, enables strong cavity-induced modifications of reaction rates. Outside of the cavity the reaction is as usual D+H₂→$DH+H. However, inside the cavity another type of reactions take place where D+H$_2→DH+H+Eₚₕₒₜₒₙ, where Eₚₕₒₜₒₙ=ωcav. Our results show that HER is an ideal platform to make a significant step toward closing the gap between theory and experiment in polariton chemistry.