Reaction Dynamics of the H + HeH⁺ → He + H₂ ⁺ System

Area of Science:

• Chemical Physics
• Theoretical Chemistry
• Reaction Dynamics

Background:

• Understanding ion-molecule reactions is crucial in astrochemistry and plasma physics.
• The H + HeH+ reaction is a fundamental system for studying reaction dynamics.
• Accurate potential energy surfaces (PESs) are essential for reliable theoretical predictions.

Purpose of the Study:

• To investigate the reaction dynamics of H + HeH+ → He + H2+ in its electronic ground state.
• To compare the influence of two different PES representations on reaction outcomes.
• To assess the accuracy requirements for PESs based on the type of observable analyzed.

Main Methods:

• Utilized two distinct potential energy surface (PES) representations.
• The first PES employed a kernel and neural network representation of UCCSD-(T) data.
• The second PES (cR-PES) corrected an artificial barrier using full configuration interaction data.

Main Results:

• Both PESs yielded comparable state-averaged rate coefficients (k ≈ 2 × 10^-9 cm^3/molecule/s at 10 K).
• Calculated rates align with Langevin rates but exceed experimental ion cyclotron resonance (ICR) values.
• Differences between PESs became apparent in state-selected, temperature-dependent rate coefficients and product vibrational states.

Conclusions:

• Accurate, globally valid PES representations are necessary for state-resolved properties.
• More approximate PESs may suffice for state-averaged observables.
• The study underscores the importance of PES accuracy depending on the specific chemical dynamics being investigated.