I am interested in learning about which light sources are used to determine the optical constants (the n and k values) of minerals over large wavelength ranges (say from the UV to the FIR).
A method that is often brought up, also in modern industrial applications, is ellipsometry. The principles of measurment are simple enough, but of course experimental challenges exist. I was particularly stunned to learn that some mineralogic data seems to have continuous wavelength coverage at say 1 Å resolution.
Is this done with laser combs? What were older light sources that gave a large wavelength coverage? Was it always some atomic lamp sources that provided many lines, or can you even just 'shine' a blackbody spectrum through a wavelength filter and determine n and k with those?