Three-body association of CO+ and N2. The case for a chemical bond

Hamilton, Bierbaum and Leone recently reported a very efficient vibrational quenching of CO⁺ (v) by N₂, only about six collisions being required for quenching at 300 K. This is an exceedingly efficient quenching process in the light of recent systematic studies of diatomic molecular ion vibrational quenching. To probe further the CO⁺?N₂ interaction, the rate coefficient for three-body association of CO⁺ and N₂ with He as third body was measured and is very large, being 2.1 × 10^?29 cm⁶ s^?1 at 298 K and 1.8 × 10^?28 cm⁶ s^?1 at 80 K. Both the efficient quenching and the rapid association imply a strong interaction between CO⁺ and N₂, much stronger than the expected ≈ 0.2 eV electrostatic potential well depth. These experiments indicate a “chemical bonding” interaction between CO⁺ and N₂, with a well depth as large as 1 eV.