Scientists show a way to speed or slow reactions using tiny mirror gaps

Researchers at the University of Rochester have uncovered a detailed explanation for how chemical reaction rates can be controlled without traditional methods like heat, light, or added chemicals, by exploiting a quantum effect called vibrational strong coupling (VSC). This phenomenon occurs when molecules are placed inside an optical microcavity—an extremely tiny gap between gold-coated mirrors—that alters the electromagnetic environment around the molecules. The interaction between molecular vibrations and confined light fields within this cavity can either speed up or slow down reactions by changing how energy is exchanged between molecules and their surroundings, effectively tuning reaction rates by adjusting the coupling strength. This discovery resolves a long-standing mystery about VSC, first observed in 2016, where reaction speeds changed under these conditions despite constant temperature and light. The University of Rochester team combined quantum mechanics with large-scale simulations to develop a model explaining when and how VSC occurs and how it can be controlled. Their findings suggest that manipulating the quantum environment, rather than the molecules themselves, offers a new, energy-efficient