Diffuse photon remission associated with the center-illuminated-area-detection geometry. III. Perspectives on the patterns of saturation

Understanding scattering insensitiveness in diffuse reflectance spectroscopy (DRS) will be useful to enhancing the spectral specificity to absorption. In DRS based on center-illuminated-area-detection (CIAD), the scattering response can saturate as the relative strength of scattering with respect to the collection size, represented by a dimensionless reduced scattering, increases over a threshold. However, the formation of saturation versus the same range of dimensionless reduced scattering may differ between a fixed reduced scattering over an increasing collection size (case 1) and an increasing reduced scattering over a fixed collection size (case 2), due to the absorption. Part III demonstrates the differences of the scattering saturation as well as the effect of absorption on it in the CIAD geometry between the two cases while assessed over the same range of the dimensionless reduced scattering. A model allows predicting the absorption-dependent levels of saturation and the corner parameters of saturation transition. When assessed for the absorption coefficient to vary over [0.001,0.01,0.1,1]