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Fourier transform infrared spectroscopy (FTIR) [1] is a technique used to obtain an infrared spectrum of absorption or emission of a solid, liquid, or gas. An FTIR spectrometer simultaneously collects high-resolution spectral data over a wide spectral range.
The sample, liquid or solid, is placed into the sample cup which is inserted into the photoacoustic cell which is then sealed for the measurement. The sample may be one solid piece, powder or basically in any form for the measurement. For example, a piece of rock can be inserted into the sample cup and the spectrum measured from it. [citation ...
The accessibility, rapid sample turnaround and ease of use of ATR with Fourier transform infrared spectroscopy (FTIR) has led to substantial use by the scientific community. This evanescent effect only works if the crystal is made of an optical material with a higher refractive index than the sample being studied.
Reflection-absorption FTIR: Sample is usually prepared as a thick block and is polished into a smooth surface. [4] As the IR beam strikes the sample surface, some of the energy is absorbed by the top layer (<10 μm) of the bulk sample. The altered incident beam is then reflected and carry the composition information of the targeted surface area.
The ratio of the "sample spectrum" to the "background spectrum" is directly related to the sample's absorption spectrum. Accordingly, the technique of "Fourier-transform spectroscopy" can be used both for measuring emission spectra (for example, the emission spectrum of a star), and absorption spectra (for example, the absorption spectrum of a ...
Both groups used a conventional Fourier transform infrared spectrometer (FTIR) equipped with a broadband thermal source, the radiation was focused near the tip of a probe that was in contact with a sample. The Lancaster group obtained spectra by detecting the absorption of infrared radiation using a temperature sensitive thermal probe.
The most common mineral oil is Nujol, which is essentially a liquid paraffin based solution and when used for mulling, strong carbon to hydrogen bond absorptions are exhibited in the infrared spectrum. The carbon to hydrogen bond absorptions that may be present in the sample itself are masked by those from the Nujol mulling agent.
nano-FTIR absorption and far-field FTIR (ATR modality) spectra measured on the same polymer sample show great agreement. Placement of the sample stage into one of the interferometer's arms (instead of outside of the interferometer as typically implemented in conventional FTIR ) is a key element of nano-FTIR.