- Industry: Chemistry
- Number of terms: 265
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A spectral manipulation technique used to reduce the amount of noise in a spectrum. It works by calculating the average absorbance (or transmittance) of a group of data points called the “smoothing window,” and plotting the average absorbance (or transmittance) versus wavenumber. The size of the smoothing window determines the number of data points to use in the average, and hence the amount of smoothing.
Industry:Chemistry
The spectrum that is obtained after Fourier transforming an interferogram. Single beam spectra contain features due to the instrument, the environment, and the sample.
Industry:Chemistry
Spectral features that appear to the sides of an absorbance band as undulations in the baseline. Sidelobes are caused by having to truncate an interferogram, as a result of finite scan distance, and can be removed from a spectrum by multiplying the spectrum’s interferogram by an apodization function.
Industry:Chemistry
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
