Impact of long-range attraction on desorption kinetics

Area of Science:

• Surface science
• Physical chemistry
• Materials science

Background:

• Desorption is fundamental to many natural and technological processes.
• First-order kinetics, assuming non-interacting adsorbates, is often a simplification.
• Adsorbate interactions significantly complicate desorption dynamics, especially in ordered structures.

Purpose of the Study:

• To investigate the desorption kinetics of 3-nitrophenol from calcite surfaces.
• To understand the influence of molecular interactions on desorption behavior.
• To identify factors governing desorption rate changes.

Main Methods:

• Isothermal desorption experiments.
• Dynamic atomic force microscopy (AFM) for real-time monitoring.
• Ultrahigh vacuum conditions.

Main Results:

• Two distinct desorption regimes were observed: an initial linear decrease in coverage (constant rate) followed by a sharp increase at lower coverages.
• A critical island width was identified as the transition point between these regimes.
• A long-range attractive interaction between molecules is proposed to explain the accelerated desorption at critical island widths.

Conclusions:

• Desorption kinetics are significantly influenced by adsorbate interactions, deviating from simple first-order models.
• The observed phenomenon of dual desorption regimes is likely general for systems with interactions beyond nearest-neighbor attraction.
• Understanding these complex desorption dynamics is crucial for applications involving molecular films on surfaces.