The author is with U.S. Army Armament Research & Development Command, Chemical Systems Laboratory, Research Division, Aberdeen Proving Ground, Maryland 21010.
Hugh R. Carlon, "Contributions of particle absorption to mass extinction coefficients (0.55–14
μm) of soil-derived atmospheric dusts," Appl. Opt. 19, 690-693 (1980)
Mass extinction coefficients of soil-derived atmospheric dusts often are determined largely by
the absorption (rather than scattering) by individual particles, especially at longer IR
wavelengths. Under many conditions, reasonable estimates of mass extinction coefficients of dusts
can be made from absorption coefficients without the need for detailed knowledge of particle optical
constants to perform, e.g., Mie calculations. This paper discusses absorption coefficients of dusts
in the visible and IR wavelengths and the physical mechanisms of dust aerosol generation determining
that portion of extinction attributable to absorption in a given dust cloud. Some soils, especially
clays, can produce dust clouds that are almost pure absorbers at longer IR wavelengths.
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Calculated from Eqs. (3) and (4) for the Rayleigh case
(Du ≪ λ).
For the Mie and geometric scattering cases, the interrelationships between
kλ and
αAλ are more complex (see
Ref. 13), and other techniques for the approximation of
extinction coefficients apply (see Ref. 3). The values shown
in parentheses are calculated using Eqs. (3) and
(4) but would be approximately correct only for fine
natural aerosol particles, e.g., the left-hand mode of the dashed curve in Fig. 2.
Probably a good approximation even at λ = 1.06 μm, since
soot typically is composed of particles with diameters predominantly near
Du = 0.1 μm, and the
Rayleigh case (Du ≪ λ) applies.
Calculated from Eqs. (3) and (4) for the Rayleigh case
(Du ≪ λ).
For the Mie and geometric scattering cases, the interrelationships between
kλ and
αAλ are more complex (see
Ref. 13), and other techniques for the approximation of
extinction coefficients apply (see Ref. 3). The values shown
in parentheses are calculated using Eqs. (3) and
(4) but would be approximately correct only for fine
natural aerosol particles, e.g., the left-hand mode of the dashed curve in Fig. 2.
Probably a good approximation even at λ = 1.06 μm, since
soot typically is composed of particles with diameters predominantly near
Du = 0.1 μm, and the
Rayleigh case (Du ≪ λ) applies.