Quantum-State Controlled Formation of Cosmically Relevant Metallic Molecular Ions

Metal-containing molecular ions are fundamentally important in both terrestrial and interstellar chemistry, yet their formation mechanisms have been largely unexplored experimentally. To address this lack of fundamental understanding of how these ions are created in space, we conducted an experimental study of a quantum-state-controlled reaction between Ca^{+} and C_{2}H_{2} to investigate a potential unifying mechanism for the formation of metallic molecules. By tuning the quantum-state populations of laser-cooled Ca^{+}, we demonstrate precise control over reactivity. Our results reveal a single ionic product, CaCCH^{+}, providing valuable insights into the mechanisms underlying the formation of metal-containing ions in space.