Molecular interactions with ice: molecular embedding, adsorption, detection, and release

Area of Science:

• Surface Science
• Physical Chemistry
• Astrochemistry

Background:

• The interaction of atomic and molecular species with water and ice is crucial in chemistry.
• Previous work showed translational energy activates embedding of Xe and Kr atoms into ice surfaces.

Purpose of the Study:

• To investigate the embedding of inert molecular species into amorphous solid water.
• To compare the embedding behavior of different molecules (CF4, SF6) and atoms (Xe, Kr) based on translational energy and molecular properties.

Main Methods:

• Experiments involving high-energy (≥3 eV) translational impacts of CF4 and SF6 molecules onto amorphous solid water.
• Comparison of embedding probabilities and rates with previously studied Xe and Kr atoms.
• Analysis of factors influencing embedding, including translational energy, van der Waals radius, and momentum.

Main Results:

• CF4 molecules with high translational energy embed in amorphous solid water, with embedding probability lower than Xe.
• SF6 molecules did not embed at energies where CF4 and Xe did, indicating embedding rate order: Xe > CF4 > SF6.
• Embedding depth is limited to less than four ice layers, and some embedded species can escape before ice desorption.

Conclusions:

• Energetic ballistic embedding is a general phenomenon for trapping species in ice.
• Translational energy, momentum, and molecular size are key factors governing embedding efficiency.
• Findings have implications for environmental science, trace gas management, and understanding astrophysical icy bodies.