An accurate 5D potential energy surface for H₃O⁺-H₂ interaction.

Area of Science:

• Astrochemistry
• Quantum Chemistry
• Spectroscopy

Background:

• Understanding interstellar oxygen chemistry relies on modeling hydronium ion (H₃O⁺) spectra.
• Collisional excitation processes involving H₃O⁺ and interstellar molecules are not well understood.
• Accurate potential energy surfaces (PES) are essential for studying these collisional interactions.

Purpose of the Study:

• To compute the five-dimensional rigid-rotor potential energy surface (PES) for the H₃O⁺-H₂ system.
• To provide a crucial component for quantum scattering calculations of H₃O⁺ in interstellar environments.
• To investigate the dissociation energies of H₃O⁺-H₂ nuclear spin isomers.

Main Methods:

• Employed explicitly correlated coupled-cluster theory [CCSD(T)-F12] with an augmented correlation-consistent valence triple zeta (aug-cc-pVTZ) basis set.
• Calculated a five-dimensional rigid-rotor potential energy surface (PES) for the H₃O⁺-H₂ interaction.
• Fitted the ab initio potential using an angular expansion for use in quantum scattering codes.

Main Results:

• Determined a potential energy surface (PES) with a significant well depth of approximately 1887.2 cm⁻¹.
• Successfully fitted the ab initio PES for efficient use in quantum scattering simulations.
• Computed dissociation energies for various nuclear spin isomers of the H₃O⁺-H₂ complex.

Conclusions:

• The computed H₃O⁺-H₂ PES is a vital step towards understanding interstellar oxygen chemistry through collisional excitation.
• This work provides essential data for future theoretical and observational studies of H₃O⁺ in space.
• The calculated dissociation energies offer insights into the stability of H₃O⁺-H₂ complexes in different isomeric forms.