Quantum Zeno Effect in Radical-Ion-Pair Recombination Reactions

Radical-ion pairs are ubiquitous in a wide range of biochemical reactions, ranging from photosynthesis to magnetic sensitive chemical reactions underlying avian magnetic navigation. We here show that the charge recombination of a radical-ion-pair is a continuous quantum measurement process that interrogates the spin state of the pair. This naturally leads to the appearance of the quantum Zeno effect, explaining a large amount of data on unusually long-lived radical-ion-pairs.