Praying Mantis diffuse reflectance accessory

Fig. 14. Praying Mantis diffuse reflectance accessory. (Reprinted courtesy of Harrick Scientific Inc.)...

Diffuse reflection spectroscopy (UV-DRS). UV-Vis diffuse reflectance spectra were recorded in a Varian Cary 5 spectrophotometer (Harrick Scientific) with a diffuse reflectance accessory of Praying Mantis geometry. The samples were set in holds with 2 mm thickness. The spectra were recorded in the 200 nm and 800 nm range with a scanning speed of 1800 mm.min at room temperature against supports as reference. 

UV/VIS-DRS measurements were performed using a Cary 400 UV/VIS spectrometer (Varian) equipped with a diffuse reflectance accessory (praying mantis, Harrick). The reflectance spectra were converted into the Kubelka-Munk function F(R) which is proportional to the absorption coefficient for low values of F(R). Spectra were deconvoluted into Gaussian bands using the GRAMS/386 program (Galactic Industries Corporation). 

Figure 4.28. Optical diagram of Praying Mantis (Harrick Scientific Inc.) diffuse-reflectance accessory Mi, M2, M5, Me — plane mirrors Ms, M4 — 6 1 90° off-axis focusing and collecting ellipsoids. Sample is placed at position S. Adapted, by permission, from K. Moradi, C. Depecker, and J. Corset, Appl. Spectrosc. 48,1491 (1994), p. 1492, Fig. 2. Copyright 1994 Society for Applied Spectroscopy.

Solids can be measured in transmission or reflection (reflectance) modes. Both specular reflection and diffuse reflection are used. Diffuse reflection accessories include the Praying Mantis from Harrick Scientific Products, Inc., and a variety of integrating spheres available from most major instrument companies. Specular reflection is used for highly reflective materials diffuse reflectance for powders and rough surfaced solids. Materials characterization relies heavily on techniques like these. 

Adsorption of CO and mixtures of CO, O2, and CO2 was performed in a diffuse reflectance Fourier transform infrared spectrometer (Thermo Nicolet) equipped with an MCFA detector, a diffuse reflectance accessory, and a high-temperature reaction chamber (Praying Mantis, Harrick). The catalyst samples were purged with helium at 250 °C for 30 min, reduced by 10% H2/He at 10 °C/ min, cooled under He flow at room temperature, and then exposed to a 5% CO/... 

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