dabsorption

Dabsorption is a theoretical quantity used in physics and engineering to describe the differential absorption of electromagnetic energy within a medium as a function of depth. It is defined as the rate of absorption per unit depth, often expressed as dA/dz, where A is the local absorbed energy density and z is the depth from the surface. The concept emphasizes spatial variation in absorption due to inhomogeneous composition, temperature gradients, or changing optical properties.

Relation to standard measures: In Beer-Lambert contexts, bulk absorption is described by an attenuation coefficient μa and path length. Dabsorption extends this by allowing μa to vary with depth. It can be used in radiative-transfer models where scattering is significant and may depend on wavelength, local intensity, and environmental factors such as temperature or chemical state. In many media, dabsorption is small near the surface but grows with depth as material properties change.

Measurement and modeling: Dabsorption is not observed directly as a single quantity; it is inferred from depth-resolved absorption measurements, such as optical coherence tomography or diffuse reflectance, and then deconvolved with scattering models to yield a depth profile. Computational approaches include layered-media analysis and Monte Carlo simulations.

Applications and status: The concept appears in theoretical modeling for optical sensing, atmospheric remote sensing, and materials science to characterize nonuniform absorbers. Its use depends on the assumptions about scattering and geometry, and there can be non-uniqueness in separating depth-dependent absorption from scattering effects.