ATR FT-IR Imaging Depth of Penetration

Depth profiling of materials using variable angle ATR spectroscopy is a well-established approach [66-69] based on the fact that the depth of penetration is a function of the angle of incidence in an ATR measurement. The relationship between the d, the wavelength of light A, the refractive indices of the ATR crystal and the sample, and 2, and the angle of incidence 9 is shown in Equation 9.1. 

Nevertheless, great potential exists in applications of variable angle of incidence ATR FT-IR imaging to heterogeneous materials, particularly to biomedical materials, for example, skin [50]. 

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