Wikipedia - Cross section (physics) scattering cross-section, $$\sigma_{\text{scat}}$$

https://doi.org/10.1351/goldbook.S05490
The @S05487@ @C01124@ per particle ($$\frac{\text{cm}^{2}}{\text{particle}}$$); $b_{\text{scat}}=n\ \sigma _{\text{scat}}$ where $$n$$ is the number concentration of particles ($$\text{particles cm}^{-3}$$) and $$\sigma _{\text{scat}}$$ is the @S05487@ cross-section. $$b_{\text{scat}}$$, the @S05487@ component of @E02293@ due to gas and particles, is measured in the atmosphere using a nephelometer. For a homogeneous atmosphere it is related in theory to the meteorological range ($$L_{\text{V}}$$): $$L_{\text{V}}=\frac{3.9}{b_{\text{scat}}}$$; $$b_{\text{scat}}$$ and $$b_{\text{abs}}$$ represent the @S05487@ and absorption coefficients per unit length for a light beam (of path length $$L$$) which has a @S05824@ (intensity) $$I_{0}$$ incident on a sample of air and $$I$$ is the transmitted @S05824@ (intensity), $$\ln (\frac{I_{0}}{I}) = L\ (b_{\text{scat}}+b_{\text{abs}})$$.
Source:
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2212 [Terms] [Paper]