Examining scattering dynamics in a state of strong rotational non-equilibrium

Molecular beam scattering is a technique where molecules of a substance are directed at a crystalline surface which reflects the molecules at an angle. In the past, many different experimental and numerical setups have been developed to study the nature of scattering dynamics.

Andric and Jenny conducted a numerical study of one such scattering case: an impinging molecule in a state of strong rotational non-equilibrium.

“We were interested to know how the energy is being redistributed between rotational and translational kinetic modes upon collision of the rotationally excited molecule with a solid surface,” said author Nemanja Andric. “The obtained numerical results allowed us to gain a better insight into the scattering dynamics, specifically the energy coupling between the translational and rotational modes during collision.”

The model featured a nitrogen molecule colliding with a smooth graphite surface, with the rotational temperature of the nitrogen varying between 300 K and 10,300 K. The researchers performed 12,000 total simulations, varying the translational and rotational speed of each molecule to get a broad range of results.

Andric and Jenny plan to experimentally verify the results from their numerical model. They hope to use this method as a tool to separate gasses that have similar mass profiles.

“The overarching aim was to investigate whether two gaseous species of similar or equal masses can be separated by selective rotational excitation of one of the species with a laser,” said Andric. “We hope that this work will provide an additional and valuable insight into the nature of scattering dynamics.”

Source: “Molecular beam scattering of a diatomic molecule from a solid surface in case of strong rotational non-equilibrium,” by Nemanja Andric and Patrick Jenny, Physics of Fluids (2022). The article can be accessed at https://doi.org/10.1063/5.0076308 .