Collision Dynamics and Solvation of Water Molecules in a Liquid Methanol Film

TL;DR

This study investigates how water molecules interact with liquid methanol films at low temperatures, revealing efficient trapping, energy loss mechanisms, and temperature-dependent incorporation, with implications for environmental and fundamental surface science.

Contribution

It provides detailed experimental insights into water-methanol collision dynamics, including energy transfer, trapping, and incorporation processes, which were not previously characterized in this context.

Findings

Water molecules are efficiently trapped by liquid methanol at 170-190 K.

Water desorption follows an Arrhenius law with specific activation energy.

Temperature influences water incorporation into methanol layers.

Abstract

Environmental molecular beam experiments are used to examine water interactions with liquid methanol films at temperatures from 170 K to 190 K. We find that water molecules with 0.32 eV incident kinetic energy are efficiently trapped by the liquid methanol. The scattering process is characterized by an efficient loss of energy to surface modes with a minor component of the incident beam that is inelastically scattered. Thermal desorption of water molecules has a well characterized Arrhenius form with an activation energy of 0.47{\pm}0.11 eV and pre-exponential factor of 4.6 {\times} 10^(15{\pm}3) s^(-1). We also observe a temperature dependent incorporation of incident water into the methanol layer. The implication for fundamental studies and environmental applications is that even an alcohol as simple as methanol can exhibit complex and temperature dependent surfactant behavior.