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2.4.3 Units for Reflectance Spectra

When displayed in absorbance units, reflectance spectra such as diffuse reflectance and ATR cannot be compared directly to absorption spectra. This is due to the fact that weak signals in absorbance spectra are enhanced in the reflected spectra (when absorbance units are used). Since most standard library spectra were collected with an absorption experiment and are stored in absorbance units, low match probabilities result when reflectance spectra are searched against common libraries. However, the reflectance spectra can be displayed in Kubelka-Munk units, which is a unit conversion that make the spectra appear similar to absorbance spectra.

One of the duties of the Intern will be to collect reflectance spectra for reference standards and compile a library in absorbance units. This will allow convenient library searches without the additional step of the mathematical conversion to Kubelka-Munk units (keeping in mind that the fewer data conversions we do, the easier it is to explain our data in court).

John S. Riley, DSB Scientific Consulting