Three-dimensional potential energy surface of Ar-CO

Area of Science:

• Chemical Physics
• Molecular Spectroscopy
• Computational Chemistry

Background:

• The Argon-Carbon Monoxide (Ar-CO) complex is a key system for understanding van der Waals interactions.
• Accurate intermolecular potential energy surfaces (PES) are crucial for predicting and interpreting spectroscopic properties.

Purpose of the Study:

• To determine a highly accurate three-dimensional intermolecular potential energy surface (PES) for the Ar-CO complex.
• To simultaneously reproduce a wide range of experimental spectroscopic data with high fidelity.

Main Methods:

• Ab initio calculations at the CCSD(T)-F12b/aug-cc-pV5Z level of theory were performed to generate an initial PES.
• A free rotor model Hamiltonian was employed to calculate vibration-rotation energies.
• Least-squares analysis was used to optimize 20 parameters of a model function against experimental spectroscopic data.

Main Results:

• The determined 3D PES accurately reproduces transition frequencies from microwave, millimeter-wave, submillimeter-wave, and infrared spectroscopy.
• Observed spectroscopic data were reproduced within their experimental accuracies, validating the PES.
• A significant reduction in the number of parameters from 46 to 20 was achieved while maintaining high accuracy.

Conclusions:

• The developed PES provides a highly accurate description of the Ar-CO intermolecular interactions.
• This work demonstrates the successful integration of high-level ab initio calculations and experimental spectroscopic data.
• The refined PES will be valuable for future theoretical and experimental studies of the Ar-CO system.