Using an Optical Centrifuge to Study CO$_{2}$ Super Rotor Collisions with He and Ar Buffer Gases

Collisions of CO$_{2}$ super rotors with Ar and He buffer gases are investigated using state-resolved high resolution transient IR absorption spectroscopy. The CO$_{2}$ super rotors are generated with an optical centrifuge that captures and accelerates the molecules to extreme rotational states with oriented angular momentum. Polarization-sensitive Doppler-broadened line profiles characterize the anisotropic kinetic energy release and show that the CO$_{2}$ super rotors behave like molecular gyroscopes. Quenching of CO$_{2}$ rotational energy is more efficient with He collisions than with Ar collisions. The experimental results are compared with quantum scattering calculations performed on the He-CO$_{2}$ and Ar-CO$_{2}$ collision systems, providing insight into the J-specific collision cross sections and rates that control the relaxation. These studies reveal how mass, velocity, and rotational adiabaticity impact angular momentum relaxation and reorientation.