Interaction of Atomic and Molecular Hydrogen with Tholin Surfaces at Low Temperatures

TL;DR

This study investigates how atomic and molecular hydrogen interact with tholin surfaces at low temperatures, revealing weak adsorption forces and providing energy barriers crucial for understanding Titan's atmospheric chemistry.

Contribution

It presents a detailed rate equation model to determine diffusion and desorption energy barriers of hydrogen on tholin surfaces at temperatures below 30 K.

Findings

Energy barriers for hydrogen diffusion and desorption are 30-60 meV.

Hydrogen interactions are dominated by weak adsorption forces.

Results inform models of Titan's atmospheric chemistry.

Abstract

We study the interaction of atomic and molecular hydrogen with a surface of tholin, a man-made polymer considered to be an analogue of aerosol particles present in Titan's atmosphere, using thermal programmed desorption at low temperatures below 30 K. The results are fitted and analyzed using a fine-grained rate equation model that describes the diffusion, reaction and desorption processes. We obtain the energy barriers for diffusion and desorption of atomic and molecular hydrogen. These barriers are found to be in the range of 30 to 60 meV, indicating that atom/molecule-surface interactions in this temperature range are dominated by weak adsorption forces. The implications of these results for the understanding of the atmospheric chemistry of Titan are discussed.