Collective Energy Transfer to a Spectator Atom via Multicenter Intermolecular Coulombic Decay

Molecular mechanisms that enable collective and upconverted energy transfer from multiple photoacceptors to a nonabsorbing spectator reaction center are highly desirable for efficient light-energy utilization. Here, we show that intermolecular Coulombic decay (ICD), a nonlocal energy-relaxation channel in photoexcited molecules, offers an avenue for such a novel energy-transfer mechanism. On irradiation of a pyridine-argon gas mixture at 266 nm and at low laser intensities, we observed a surprisingly dominant formation of argon cations. Measurements of the laser-power dependence, together with systematic studies of Ar^{+} yield versus laser intensity and molecular density, reveal that ICD mediates the collective funneling of excitation energy from multiple photoexcited pyridine molecules to a nonphotoabsorbing argon atom, leading to its ionization. The density of the reaction center offers an efficient handle to optimize this collective energy transfer. This mechanism opens new avenues in light-harvesting design and may help explain the remarkable resistance of biomolecules to photodamage.