Ytkoncentration

Ytkoncentration is a term found in some Nordic-language contexts to describe the surface concentration of a chemical species—the amount of substance present per unit area at a surface or interface. It is distinguished from bulk concentration, which is defined per unit volume. The surface concentration is commonly denoted by the symbol Γ and is typically expressed in units such as mol/m^2 or molecules/m^2.

In equilibrium, the surface concentration relates to the bulk concentration through adsorption processes. Classical models such as the Langmuir and Freundlich isotherms describe how Γ depends on the nearby bulk concentration C. For example, the Langmuir form can be written as Γ = Γmax · (K C) / (1 + K C), where Γmax is the maximum surface coverage and K is the equilibrium constant. In nonideal or heterogeneous systems, more complex isotherms or kinetic descriptions may be used, incorporating surface site availability and interactions between adsorbates.

Measurement and interpretation of ytkoncentration rely on surface-sensitive techniques. Composition and chemical state information are commonly obtained by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), Auger electron spectroscopy (AES), or low-energy ion scattering (LEIS). Quantitative or cross-validated estimates of Γ can also be derived from ellipsometry or quartz crystal microbalance with dissipation (QCM-D) data, which relate mass change to surface coverage. Spatially resolved methods such as atomic force microscopy (AFM) or scanning probe techniques can map heterogeneity in surface concentration.

Applications span catalysis, electrochemistry, corrosion science, thin-film technology, and environmental studies, where surface processes control overall behavior. Note that ytkoncentration is not widely standardized in English-language literature; the same concept is often described as surface concentration or interfacial concentration. See also adsorption, surface science, and interfacial phenomena.