Adsorptionszweig

Adsorptionszweig, or adsorption branch, is a term used in surface science to describe a specific portion of an adsorption isotherm. It represents the progression of surface coverage as the adsorbate chemical potential or the relative pressure increases at a fixed temperature. In many systems the isotherm consists of an adsorption branch and a desorption branch, which can form a hysteresis loop; the adsorption branch traces the path followed during increasing pressure.

The adsorption branch typically begins with the formation of a monolayer and can extend into multilayer adsorption or capillary condensation, depending on pore structure, temperature, and adsorbate–surface interactions. Its shape and extent provide information about surface area, pore size distribution, and interaction strength. The branch is analyzed using adsorption models such as Langmuir for monolayer coverage, BET for multilayer adsorption, and capillary condensation theories for mesoporous materials.

Experimental and theoretical methods are used to identify and interpret the adsorption branch. Gravimetric and volumetric adsorption measurements are common, often complemented by calorimetric data. The adsorption branch is especially important when interpreting hysteresis in porous materials and when assessing reversible versus metastable adsorption processes, including phase transitions within pores.

Notes on terminology: the term is more common in German-language literature and may vary in English-language sources, where phrases like “adsorption isotherm branch” or “adsorption leg” might be used. Nevertheless, the underlying concept—the path of adsorption on the rising portion of the isotherm—remains consistent across sources.