Inelastic vibrational dynamics of CS in collision with H₂ using a full-dimensional potential energy surface.

Area of Science:

• Chemical Physics
• Quantum Scattering Theory
• Computational Chemistry

Background:

• Accurate potential energy surfaces (PES) are essential for understanding molecular collisions.
• Previous studies on CS-H2 interactions often employed approximations like the rigid-rotor model.
• Investigating vibrational quenching is critical for astrophysical models.

Purpose of the Study:

• To compute a high-accuracy six-dimensional (6D) potential energy surface (PES) for the CS-H2 system.
• To perform full-dimensional quantum close-coupling scattering calculations for rotational and vibrational transitions.
• To provide state-to-state cross sections and rate coefficients for astrophysical applications.

Main Methods:

• High-level electronic structure theory was used for PES computation.
• A hybrid invariant polynomial method was employed for PES fitting.
• Full-dimensional quantum close-coupling scattering calculations were performed.

Main Results:

• Calculated state-to-state cross sections and rate coefficients for rotational transitions in CS induced by H2.
• For the first time, computed cross sections and rate coefficients for vibrational quenching transitions of CS by H2.
• Results were obtained for collision energies from 1 to 3000 cm⁻¹ and temperatures from 5 to 600 K for both para- and ortho-H2.

Conclusions:

• The developed 6D PES provides a reliable foundation for CS-H2 collision dynamics.
• The computed rate coefficients are valuable for astrophysical models, particularly in understanding the chemical evolution of interstellar environments.
• This work advances the understanding of molecular energy transfer processes in low-temperature environments.