Extinction Cross Section

Extinction for simplicity we consider homogeneous spherical dust particles of radius a and introduce the cross section for extinction a2q ext where q ext is the efficiency factor for extinction.

Extinction cross section. Same as radiance but per unit wavelength range j m 2 s. The total extinction cross section is proportional to the optical density of a sample measured by standard uv visible spectroscopy and the calculator provides information on how the scattering and absorption components contribute to the total extinction. Note that light in this context is described as consisting of particles i e photons.

To compare the effectiveness of nanoparticles of different sizes for real biomedical applications size normalized optical cross sections or per micron coefficients are calculated. More generally the term cross section is used in physics to quantify the probability of a certain particle particle interaction e g scattering electromagnetic absorption etc. The si unit of molar attenuation coefficient is the square metre per mole m 2 mol but in practice quantities are usually expressed in terms of m 1 cm 1 or l mol 1 cm 1 the latter two units are both.

This tool uses mie theory to calculate the optical cross sections of single component or core shell spherical nanoparticles. Customary usage in radar describes the attenuation cross section as the area that when multiplied by the power density of incident plane wave radiation gives the power removed from the beam by absorption and scattering for a propagation medium consisting of a dispersion of scattering and absorbing objects the volume extinction coefficient m 2 m 3 or m 1 at a given location in the medium. In physics the cross section is a measure of probability that a specific process will take place in a collision of two particles.

The extinction cross is an optical phenomenon that is seen when trying to extinguish a laser beam or non planar white light using crossed polarizers ideally crossed 90 rotated polarizers block all light since light which is polarized along the polarization axis of the first polarizer is perpendicular to the polarization axis of the second. Such small cross sections are very challenging to measure with sufficient accuracy. Same as flux but for a unit area with a fixed orientation j m 2 s 1 e λ spectral irradiance.

Absorption cross section is a measure for the probability of an absorption process. The optical depth along a line sight with volumetric dust density n d is then extinction in magnitudes a is defined in terms of the. The molar attenuation coefficient is a measurement of how strongly a chemical species attenuates light at a given wavelength it is an intrinsic property of the species.

This means that cross sections as small as 10 20 cm2 or even smaller are potentially interesting.