Why is it useful to dilute samples for Diffuse Reflection experiments?
The specular reflectance component in diffuse reflectance spectra causes changes in band shapes, their relative intensity, and in some cases it is responsible for complete band inversions (restrahlen bands). Dilution of the sample with a non-absorbing matrix minimizes these effects (particle sizes and loading also play an important role). Refractive index effects result in specular reflectance contributions (spectra of highly reflecting samples will be more distorted by the specular reflectance component). This can be significantly reduced by sample dilution. Other Factors: Particle Size – reducing the size of the sample particles reduces the contribution of reflection from the surface. Small particles improve the quality of spectra (narrow bandwidths and better relative intensity). The recommended size of the sample/matrix particles is 50 micrometers or less (comparable to the consistency of the finely ground flour). Homogeneity – samples prepared for diffuse reflectance measurements
