Vibrational Quantum-State-Controlled Reactivity in the O ₂ ⁺ + C ₃ H ₄ Reaction

Quantum-state-controlled reactivity is a long-standing goal in the field of physical chemistry. In this work, we explore the vibrational-state-dependent behavior of the ion-molecule reaction between O₂⁺ in distinct vibrational states and two isomers of C₃H₄, allene (H₂C₃H₂) and propyne (H₃C₃H). While most products are formed regardless of the vibrational state of O₂⁺, the branching ratios are influenced by vibrational excitation, and a new product, C₂O⁺, appears exclusively in the excited-state reactions. This selective formation of C₂O⁺ demonstrates that vibrational excitation can effectively activate a reaction pathway, providing direct evidence of quantum-state control in the reactivity. These results represent an important step toward the goal of quantum-state-controlled chemistry in molecular systems.