A new ab initio potential energy surface for the NH-He complex.

Area of Science:

• Chemical Physics
• Quantum Chemistry
• Spectroscopy

Background:

• Understanding intermolecular forces is crucial for molecular dynamics.
• Accurate potential energy surfaces (PES) are essential for theoretical simulations.
• The NH-He system is a benchmark for studying open-shell van der Waals interactions.

Purpose of the Study:

• To compute a new three-dimensional potential energy surface (PES) for the NH-He van der Waals system.
• To investigate the spectroscopy of the NH-He complex.
• To calculate collisional excitation cross sections and rate coefficients for NH by He.

Main Methods:

• Coupled cluster calculations with augmented correlation-consistent basis sets.
• Extrapolation to the complete basis set limit.
• Close-coupling calculations for collisional dynamics.

Main Results:

• A new, accurate 3D PES for NH-He was generated.
• Calculated rotational constants for the NH-He complex show good agreement with experimental data.
• State-specific collisional excitation cross sections and rate coefficients were computed for NH by He.

Conclusions:

• The new PES accurately describes the NH-He interaction.
• Theoretical predictions for NH-He spectroscopy and collisional properties are in good agreement with experiments.
• This work provides valuable data for astrophysical and atmospheric chemistry applications.