To test the characteristics of the new spectrograph for Raman
spectroscopy ( wavelength range available, sensitivity, vignetting,
shape of spectra, spectral background...) I have chosen some plastic
materials because the carbon containing molecules give vibration spectra
at higher frequency than minerals and with such materials, the CH band
around 3000 cm-1 can also be examined. See results on the
Spectrum of the cover of a lab polyethylene
Two spectra have been recorded in the low and high wavelength range.
This spectrum is a typical polyethylene spectrum as can be found in the
literature. The blue curve is C-C stretching vibrations and CH bending
modes. Red curve is the C-H stretching vibrational modes.
spectrum, Raman low range, as processed in Visual Spec program (scale in
This raw spectrum shows the improvement in the
baseline and the absence of vignetting compared to spectra given by the
H20 monochromator used in the first design of the Raman microscope.
Processed spectrum of a polypropylene
This Raman spectrum is not a pure polypropylene but made of two
components: the part above 700 cm-1 is really the
polypropylene. The lower part below 700 cm-1 is a
mineral filler made of TiO2 , a mixture of rutile and anatase.
The red spectrum has been recorded with a 25µ slit to improve the
resolution, it shows the details of the C-H stretching band.
Polymethyl methacrylate (PMMA
This spectrum from a clear plastic disk used for the
presentation of minerals samples in display cabinets is identified as PMMA. It illustrates again the better performances of the new
spectrograph compared to the H-20 which was unable to record spectra from
200 to 1800 cm-1. Here we can see the vibration of the ester
C=O bond at 1730 cm-1.
Spectrum of a green
plastic Perrier bottle of mineral water.
I have'nt tried yet to identify this polymer.