Interaction of NaI with solid water and methanol

Area of Science:

• Surface Science
• Physical Chemistry
• Materials Science

Background:

• Understanding the behavior of ionic compounds like sodium iodide (NaI) on different surfaces is crucial for various chemical and physical processes.
• Amorphous solid water (ASW) and methanol (MeOH) serve as relevant model systems for condensed phases.

Purpose of the Study:

• To investigate the interaction of NaI with ASW and MeOH films.
• To determine the surface segregation behavior of iodide ions.
• To analyze the electronic properties and binding energies upon NaI deposition.

Main Methods:

• Metastable Impact Electron Spectroscopy (MIES)
• Ultraviolet Photoelectron Spectroscopy (UPS) using HeI radiation
• Temperature Programmed Desorption (TPD)

Main Results:

• NaI layers were prepared on ASW and MeOH films at ~105 K and annealed up to ~200 K.
• Surface segregation of iodide was observed on ASW, consistent with aqueous solution behavior.
• No surface segregation of iodide was observed on MeOH, mirroring liquid methanol interactions.
• Electronic properties (ionization potentials, optical band gaps) and water binding energies were determined.

Conclusions:

• The interaction of NaI with ASW and MeOH exhibits distinct surface segregation patterns.
• Observed behaviors align with predictions based on NaI interactions with aqueous and liquid methanol solutions.
• The study provides insights into the electronic properties and binding characteristics of NaI on these condensed phases.