FTIR, attenuated total reflectance data collection

An infrared spectrum is a plot of percent radiation absorbed versus the frequency of the incident radiation given in wavenumbers (cm ) or in wave length ( xm). A variation of this method, diffuse reflectance spectroscopy, is used for samples with poor transmittance, e.g. cubic hematite crystals. Increased resolution and sensitivity as well as more rapid collection of data is provided by Fourier-transform-IR (FTIR), which averages a large number of spectra. Another IR technique makes use of attenuated total reflectance FTIR (ATR-FTIR) often using a cylindrical internal reflectance cell (CIR) (e.g. Tejedor-Tejedor Anderson, 1986). ATR enables wet systems and adsorbing species to be studied in situ. 

Figure 3.13. (d) Time-resolved attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectra collected during arsenic (As) oxidation on random stacked bimessite (RSB). Peaks represent the oxidation product, arsenate, adsorbed at the RSB surface. (Z ) As oxidation kinetic data collected on RSB (O) on hexagonal bimessite (H-Bi) ( ) during a batch experiment. Inset shows the peak height versus time plot for the spectra seen in the top panel, illustrating the higher time resolution achievable with rapid-scan ATR-FUR spectroscopy. (From Borda and Sparks, unpublished data, 2006.)... 

The composition at various positions on the lens was measured by attenuated total reflectance Fourier transform infrared (ATR-FTIR) microspectroscopy. The composition was determined from the normalized intensity of characteristic peaks for SAN17 at 698 cm and for PMMA at 1727 cm Figure 2a. Data were collected with a Nexus 870 FT-IR bench coupled to a continuum microscope (Thermo Nicolet, Madison, WI). Spectra were collected at a resolution of 2 cm" for 32 scans. Individual spectra were collected at 320 oon intervals over the lens surface. From the compositions, the refractive index at each point was calculated. 

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