ForwardScatterMessungen

Forward scatter refers to the scattering of electromagnetic radiation in directions close to the original propagation direction after interaction with a medium or particulate matter. It is typically described by the angular distribution of scattered light, often expressed through the differential cross section dσ/dΩ as a function of the scattering angle θ relative to the incident beam. In many contexts, forward scattering emphasizes small angles near θ = 0, where interference from the scatterers produces a strong forward peak. The exact pattern depends on particle size, refractive index, wavelength, and shape; small particles tend toward a broader, less forward-peaked distribution (as described by Rayleigh theory), while larger particles exhibit a pronounced forward peak (as predicted by Mie theory).

In flow cytometry and related techniques, forward scatter is the signal detected downstream from the sample as light is scattered in the forward direction. This FSC signal is commonly used as a proxy for cell or particle size, especially when paired with side scatter measurements that reflect internal complexity or granularity.

In atmospheric optics and remote sensing, forward scattering influences radiative transfer and visibility. Forward-scattered light can traverse a medium with relatively less attenuation than heavily scattered light at larger angles, though multiple scattering can complicate interpretation. Phase functions are used to model the angular dependence of forward scattering for aerosols and droplets and are essential in simulations of lidar, climate models, and optical imaging through scattering media.

Limitations include sensitivity to instrument geometry, detector placement, particle shape, and multiple scattering effects, which can complicate the extraction of intrinsic particle properties from forward-scattered signals.