Communication: Classical threshold law for ion-neutral-neutral three-body recombination

Area of Science:

• Physical Chemistry
• Atomic and Molecular Physics
• Chemical Physics

Background:

• Classical trajectory calculations are crucial for understanding molecular collisions.
• Low-energy ion-neutral-neutral ternary processes are fundamental in various chemical environments.
• Previous methods may not fully capture the dynamics of three-body recombination at ultracold temperatures.

Purpose of the Study:

• To apply a recent classical trajectory method to study ion-neutral-neutral ternary processes at low collision energies.
• To derive and numerically verify a threshold law for three-body recombination cross sections.
• To investigate the nature of products formed, specifically weakly bound dimers, and their relative abundance.

Main Methods:

• Utilized a recently developed classical trajectory calculation method for three-body collisions.
• Simulated ion-neutral-neutral ternary processes within a low energy range (0.1 mK–10 mK).
• Analyzed the resulting cross sections to identify and verify a threshold law.

Main Results:

• A threshold law for the three-body recombination cross section was successfully derived and numerically corroborated.
• The derived law predicts the formation of weakly bound dimers.
• Binding energies of these dimers are comparable to the collision energies of the participating particles.

Conclusions:

• At ultracold temperatures, molecular ions are predicted to be the predominant products in these ternary collisions.
• The findings provide insights into recombination dynamics in ion-molecule systems.
• The study validates the applicability of the new trajectory method for low-energy chemical dynamics.