Mica, visible-IR transmission
The narrow absorption at 1400nm is from OH: the second harmonic of the fundamental stretch mode at 3650cm-1. A weak absorption at 960nm in the spectrum both samples - but overlayed by interference fringes - is the third harmonic of OH. I think the strong absorption at 2200nm is due the Al - OH stretch vibration.
For more information about the various chemical formulae of mica, see: en.wikipedia.org/wiki/Mica
The interference fringes (ripples) seen in the thicker of these samples is due to the cleavage planes within the mica and varies from place to place - the dominant one here is 10 microns thick. The 'thickening' of the orange line spectrum is due to fine, but resolved fringes between 700 and 1000nm and corresponds to interference between the top and bottom surfaces of this 170 micron thick sample.
Mica, visible-IR transmission
The narrow absorption at 1400nm is from OH: the second harmonic of the fundamental stretch mode at 3650cm-1. A weak absorption at 960nm in the spectrum both samples - but overlayed by interference fringes - is the third harmonic of OH. I think the strong absorption at 2200nm is due the Al - OH stretch vibration.
For more information about the various chemical formulae of mica, see: en.wikipedia.org/wiki/Mica
The interference fringes (ripples) seen in the thicker of these samples is due to the cleavage planes within the mica and varies from place to place - the dominant one here is 10 microns thick. The 'thickening' of the orange line spectrum is due to fine, but resolved fringes between 700 and 1000nm and corresponds to interference between the top and bottom surfaces of this 170 micron thick sample.