Molecular square dancing in CO-CO collisions

Knowledge of rotational energy transfer (RET) involving carbon monoxide (CO) molecules is crucial for the interpretation of astrophysical data. As of now, our nearly perfect understanding of atom-molecule scattering shows that RET usually occurs by only a simple “bump” between partners. To advance molecular dynamics to the next step in complexity, we studied molecule-molecule scattering in great detail for collision between two CO molecules. Using advanced imaging methods and quasi-classical and fully quantum theory, we found that a synchronous movement can occur during CO-CO collisions, whereby a bump is followed by a move similar to a “do-si-do” in square dancing. This resulted in little angular deflection but high RET to both partners, a very unusual combination. The associated conditions suggest that this process can occur in other molecule-molecule systems.

Rotational Energy Transfer Non-Reactive Hydrogen-Hydrogen Collisions at Low Temperatures of Astrophysical Interest

We perform a pure quantum-mechanical calculation for the non-reactive scattering in atomic and molecular hydrogen-hydrogen collisions, i.e. H2+H2 and H+H2. Different potential energy surfaces (PESs) for the H3 and H4 atomic systems have been used. The rigid rotor model of the diatomic molecules, i.e. when the distance between hydrogen atoms is fixed at some average equilibrium value, has been applied in our calculation. After this preparatory stage the astrophysical H2-cooling function can be estimated at different astrophysical conditions and temperatures.