| The spectrometer is a vacuum instrument and is equipped for collection of spectra over the NIR, MIR and FIR ranges (15000 to 50 cm-1) depending on the combination of beamsplitters and detectors. Specialised sampling accessories include:
- Attenuated Total Reflection (ATR):A versatile and powerful sampling technique that requires minimal or no sample preparation. The sample is placed in close contact with a crystal of a particular refractive index and is internally reflected at the surface which is in contact with the sample. At the point of reflection, some energy is lost to the sample, and this corresponds to absorption bands of the sample. ATR is used for analysis of materials that are strong absorbers and can provide information about the surface properties of a material.
- Diffuse Reflectance Infrared Fourier Transform (DRIFT): Infrared light is directed onto the surface of a solid (finely ground) and numerous reflections can occur including specular, diffuse, refraction, diffraction. True diffuse reflection is the radiation which penetrates into the sample and then emerges. DRIFT spectroscopy offers a number of advantages including minimal or no sample preparation, high sensitivity, the ability to analyse non-reflective materials (highly opaque or weakly absorbing) and irregular surfaces or coatings.
- Grazing Angle (GA): The grazing angle accessory is used for analysis of sub-micron layers and liquid-air interfaces. It is a highly sensitive technique that can also be used for molecular orientation studies.
- Photoacoustic (PA): The sample is enclosed in a gas filled cell equipped with a microphone. The sample is then irradiated with IR radiation. As the sample absorbs radiation there is a periodic temperature fluctuation. The radiation is released from the sample into the surrounding gas which in crases the pressure of that gas. The pressure change is detected by the microphone and the signal is converted to a spectrum. This technique is used for the analysis of highly absorbing solid samples, either macro or micro quantity.
- Microscopy: The combination of infrared spectroscopy and light microscopy allows investigation of both the chemical and physical structure of a material. Specialised techniques such as mapping allow a two dimensional functional group map to be constructed. These maps illustrate the distribution of different chemical functional groups within a sample.
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