I would say differences in IR absorption might be used, for example, [0] [0] https://www.osapublishing.org/jnirs/viewmedia.cfm?uri=jnirs-10-4-247 https://www.o

I would say differences in IR absorption might be used, for example, [0] [0] https://www.osapublishing.org/jnirs/viewmedia.cfm?uri=jnirs-10-4-247 https://www.osapublishing.org/jnirs/viewmedia.cfm?uri=jnirs-...