Application of Kubelka‐Munk theory of diffuse reflectance to geologic problems: The role of scattering

Abstract

We have used the Kubelka‐Munk theory of diffuse reflectance to learn about the manifestations of light scattering in reflectance spectra in geologically significant situations. For wavelength‐independent scattering (dimensions of the scattering centers greater than the wavelength of the incident radiation), the band depths and shapes are related to the scattering power of the medium. For wavelength‐dependent scattering (dimensions of the scattering centers comparable to or less than the wavelength of the incident radiation), additionally found were longward shifts in band minima and a general declining trend in reflectance with increasing wavelength. This effect may be responsible for the negative slope in the near‐IR reflectance spectra of the dark regions of Mars. For both kinds of scattering, nodes are observed in sets of normalized reflectance spectra when certain conditions are satisfied.

Strength of the H2O near‐infrared absorption bands in hydrated minerals: Effects of measurement geometry

“…This definition corresponds in fact to a “Normalized Band Depth” (relative to the continuum) and will be referred as “NBD” in the rest of this manuscript. This contrasts with the definition of “Band Depth” proposed by [ Morris et al , 1982] as a simple difference of reflectance between the band and the continuum: BD( λ ) = R( λ ) − R c ( λ ).…”

Strength of the H2O near‐infrared absorption bands in hydrated minerals: Effects of particle size and correlation with albedo

“…This definition corresponds, in fact, to a normalized band depth (relative to the continuum) and is hereinafter referred to as “NBD”. Another definition of band depth was proposed by Morris et al [1982] as a simple difference of reflectance between the band and the continuum: BD( λ ) = R( λ )−R c ( λ ). In this definition, no normalization is implied.…”

Fe-Speciation in Kaolins: A Diffuse Reflectance Study

“…This formalism is well suited, because it takes into consideration light scattering as well as absorption processes (Wendlandt and Hecht, 1966). A remission function is defined as f(R~) = (1 -R~)z/ 2R~ = k/s, in which R~ is the diffuse reflectance of the sample and k and s are the absorption and scattering coefficient, respectively (Morris et al, 1982). The scattering coefficient, s, may differ between the samples as it depends on the particle size as well as on particle shape and packing.…”