- Industry: Chemistry
- Number of terms: 265
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A measure of how well an IR spectrometer can distinguish spectral features that are close together. For instance, if two features are 4 cm-1 apart and can be discerned easily, the spectrum is said to be at least 4 cm-1 resolution. Resolution in an FT-IR is mainly determined by the optical path difference.
Industry:Chemistry
A software procedure to compensate for not taking a data point exactly at ZOPD, and for frequency dependent variations caused by the beam splitter and signal amplification. The Mertz and Forman corrections are both used with the Mertz applied to double sided interferograms; this is considered in the most accurate approach.
Industry:Chemistry
The difference in optical distance that two light beams travel in an interferometer.
Industry:Chemistry
Physical distance multiplied by the index of refraction of the medium.
Industry:Chemistry
A term widely used in information theory, but here applies to the highest frequency, shortest wavelength, that can be identified in an interferogram. It is the one for which there are exactly two points per cycle. The contribution of any higher frequency, signal or noise, can be represented by some lower frequency and so will appear aliased or folded into the spectrum.
Industry:Chemistry
The process of dividing all the absorbance values in a spectrum by the largest absorbance value. This resets the Y axis scale from 0 to 1.
Industry:Chemistry
The distance that the mirror in an interferometer has moved from zero path difference.
Industry:Chemistry
This is the throughput advantage of FT-IRs over traditional spectrometers that require a slit aperture. The advantage varies as wavenumber and depends on resolution (because of slit width changes). In practice, any advantage will also depend on source dimensions.
Industry:Chemistry
An aperture placed in the beam to restrict the divergence to the maximum compatible with the selected resolution. When choosing lower resolution you can improve the S/N by opening the stop. Note that in many instances there is no physically separate stop but there will be some aperture, be it the source size, or the detector active area, that acts as the system J stop.
Industry:Chemistry
A plot of infrared detector response versus optical path difference. The fundamental measurement obtained by an FT-IR is an interferogram. Interferograms are Fourier transformed to give infrared spectra.
Industry:Chemistry
