- Отрасли: Chemistry
- Number of terms: 265
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A phenomenon that occurs when two waves occupy the same space and are in phase with each other. Since the amplitudes of waves are additive, the two waves will add together to give a resultant wave which is more intense than either of the individual waves.
Industry:Chemistry
The ideal input beam is a cylinder of light. No beam of finite dimensions can be perfectly collimated; at best there is a diffraction limit. In practice the input beam is a cone that is determined by the source size or aperture used. The degree of collimation can affect the S/N and the resolution
Industry:Chemistry
The process of adding interferograms together to achieve an improvement in signal-to-noise ratio.
Industry:Chemistry
The sharp, intense part of an interferogram. The size of the centerburst is directly proportional to the amount of infrared radiation striking the detector.
Industry:Chemistry
With no apodization, all points in an interferogram are given equal weight, up to the edges of the interferogram. If the resolution is less than the smallest linewidth in the spectrum, oscillations appear on the baseline on both sides of the peaks.
Industry:Chemistry
A spectral manipulation technique used to correct spectra with sloped or varying baselines. The user must draw a function parallel to the baseline, then this function is subtracted from the spectrum.
Industry:Chemistry
A single beam spectrum acquired with no sample in the infrared beam. The purpose of a background spectrum is to measure the contribution of the instrument and environment to the spectrum. These effects are removed from a sample spectrum by ratioing the sample single beam spectrum to the background spectrum.
Industry:Chemistry
A reflectance sampling technique. In ATR, infrared radiation impinges on a prism of infrared transparent material of high refractive index. The total internal reflectance based design assures that the light reflects off the surface of the crystal at least once before leaving it. The infrared radiation sets up an evanescent wave which penetrates a small distance above and below the crystal surface. Samples brought into contact with the surface will absorb the evanescent wave giving rise to an infrared spectrum. This sampling technique is useful for liquids, polymer films, and semisolids.
Industry:Chemistry
The spreading out of an infrared beam as it travels through the FT-IR. Angular divergence contributes to noise in high resolution spectra, and can be a limit to achievable resolution.
Industry:Chemistry
Units used to measure the amount of IR radiation absorbed by a sample. Absorbance is commonly used as the Y axis units in IR spectra. Absorbance is defined by Beer’s Law, and is linearly proportional to concentration.
Industry:Chemistry
