Quantum dynamical resonances in low-energy CO(j = 0) + He inelastic collisions

Area of Science:

• Physical Chemistry
• Chemical Physics
• Quantum Dynamics

Background:

• Resonances, quasi-bound states in van der Waals potentials, manifest as challenging-to-detect peaks in collision cross-sections.
• Experimental identification of these molecular resonances is difficult due to their subtle signatures.

Purpose of the Study:

• To fully characterize quantum-dynamical resonances in inelastic collisions of carbon monoxide (CO) with helium (He).
• To investigate CO rotational excitation (j = 0->1) at very low collision energies.

Main Methods:

• Utilized crossed-beam scattering experiments at collision energies as low as 4 cm⁻¹, corresponding to 4 K.
• Employed quantum-mechanical calculations to identify and analyze resonance structures in experimental cross-sections.

Main Results:

• Achieved a complete characterization of quantum-dynamical resonances in CO-He inelastic collisions.
• Demonstrated excellent agreement between experimental measurements and quantum-mechanical calculations.
• Validated the accuracy of potential energy surfaces for CO-He van der Waals interactions.

Conclusions:

• The validated potential energy surfaces are suitable for calculating state-to-state (de)excitation rate coefficients.
• These calculations are vital for chemical modeling of the interstellar medium at low temperatures.
• Computed state-to-state rate coefficients for CO-He collisions.