Cold collisions of highly rotationally excited CO₂ with He: The prospects for cold chemistry with super-rotors

Building on recent advances in ultrafast lasers and methods to slow molecules, an experiment is proposed to produce translationally cold CO ₂ super-rotors (j∼200) by combining an optical centrifuge with helium-buffer-gas cooling. Quantum mechanical calculations of the complex scattering length for He-CO₂ collisions demonstrate that the efficiency of rotational quenching decreases rapidly with increasing rotational excitation j in the ultracold regime. Extrapolating to helium cryogenic temperatures, rotational quenching is predicted to remain inefficient up to ∼1 K, allowing for the possible creation of a beam of translationally cold, rotationally hot molecules.