Dissociative recombination without a curve crossing

Ab initio calculations show that a curve crossing is not always needed for a high dissociative-recombination cross section. For HeH⁺, in which no neutral states cross the ion potential curve, dissociative recombination is driven by the nuclear kinetic-energy operator on adiabatic potential curves. The kinetic-energy derivative operator allows for capture into repulsive curves that are outside of the classical turning points for the nuclear motion. The dominant dissociative route is the ²Σ⁺ state leading to H(n=2) atoms. An analogous mechanism is proposed for the dissociative recombination of H₃⁺.