646:, corresponding to a maximum OPD of 10 m. The point in the interferogram corresponding to zero path difference has to be identified, commonly by assuming it is where the maximum signal occurs. This so-called centerburst is not always symmetrical in real world spectrometers so a phase correction may have to be calculated. The interferogram signal decays as the path difference increases, the rate of decay being inversely related to the width of features in the spectrum. If the OPD is not large enough to allow the interferogram signal to decay to a negligible level there will be unwanted oscillations or sidelobes associated with the features in the resulting spectrum. To reduce these sidelobes the interferogram is usually multiplied by a function that approaches zero at the maximum OPD. This so-called
836:). These detectors operate at ambient temperatures and provide adequate sensitivity for most routine applications. To achieve the best sensitivity the time for a scan is typically a few seconds. Cooled photoelectric detectors are employed for situations requiring higher sensitivity or faster response. Liquid nitrogen cooled mercury cadmium telluride (MCT) detectors are the most widely used in the mid-IR. With these detectors an interferogram can be measured in as little as 10 milliseconds. Uncooled indium gallium arsenide photodiodes or DTGS are the usual choices in near-IR systems. Very sensitive liquid-helium-cooled silicon or germanium bolometers are used in the far-IR where both sources and beamsplitters are inefficient.
501:, any energy at shorter wavelengths would be interpreted as coming from longer wavelengths and so has to be minimized optically or electronically. The spectral resolution, i.e. the separation between wavelengths that can be distinguished, is determined by the maximum OPD. The wavelengths used in calculating the Fourier transform are such that an exact number of wavelengths fit into the length of the interferogram from zero to the maximum OPD as this makes their contributions orthogonal. This results in a spectrum with points separated by equal frequency intervals.
423:
to vary the path of one beam. In this arrangement the moving mirror must not tilt or wobble as this would affect how the beams overlap as they recombine. Some systems incorporate a compensating mechanism that automatically adjusts the orientation of one mirror to maintain the alignment. Arrangements that avoid this problem include using cube corner reflectors instead of plane mirrors as these have the property of returning any incident beam in a parallel direction regardless of orientation.
469:
402:. Ideally 50% of the light is refracted towards the fixed mirror and 50% is transmitted towards the moving mirror. Light is reflected from the two mirrors back to the beam splitter and some fraction of the original light passes into the sample compartment. There, the light is focused on the sample. On leaving the sample compartment the light is refocused on to the detector. The difference in optical path length between the two arms to the interferometer is known as the
819:). The output is similar to a blackbody. Shorter wavelengths of the near-IR, 1−2.5 μm (10,000–4,000 cm), require a higher temperature source, typically a tungsten-halogen lamp. The long wavelength output of these is limited to about 5 μm (2,000 cm) by the absorption of the quartz envelope. For the far-IR, especially at wavelengths beyond 50 μm (200 cm) a mercury discharge lamp gives higher output than a thermal source.
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precision optical and mechanical components had to be solved. A wide range of instruments are now available commercially. Although instrument design has become more sophisticated, the basic principles remain the same. Nowadays, the moving mirror of the interferometer moves at a constant velocity, and sampling of the interferogram is triggered by finding zero-crossings in the fringes of a secondary interferometer lit by a
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1022:. The images contain a spectrum for each pixel and can be viewed as maps showing the intensity at any wavelength or combination of wavelengths. This allows the distribution of different chemical species within the sample to be seen. This technique has been applied in various biological applications including the analysis of tissue sections as an alternative to conventional
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the collimated beam in the interferometer. This is because convergent rays are modulated at different frequencies as the path difference is varied. Such an aperture is called a
Jacquinot stop. For a given resolution and wavelength this circular aperture allows more light through than a slit, resulting in a higher signal-to-noise ratio.
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and proteins in hydrophobic membrane environments. Studies show the ability of FTIR to directly determine the polarity at a given site along the backbone of a transmembrane protein. The bond features involved with various organic and inorganic nanomaterials and their quantitative analysis can be done
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Another minor advantage is less sensitivity to stray light, that is radiation of one wavelength appearing at another wavelength in the spectrum. In dispersive instruments, this is the result of imperfections in the diffraction gratings and accidental reflections. In FT instruments there is no direct
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The wavelength accuracy or Connes' advantage. The wavelength scale is calibrated by a laser beam of known wavelength that passes through the interferometer. This is much more stable and accurate than in dispersive instruments where the scale depends on the mechanical movement of diffraction gratings.
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has entrance and exit slits which restrict the amount of light that passes through it. The interferometer throughput is determined only by the diameter of the collimated beam coming from the source. Although no slits are needed, FTIR spectrometers do require an aperture to restrict the convergence of
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into one of the beams. Increasing the thickness of KBr in the beam increases the optical path because the refractive index is higher than that of air. One limitation of this approach is that the variation of refractive index over the wavelength range limits the accuracy of the wavelength calibration.
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in cm is equal to the reciprocal of the maximal retardation in cm. Thus a 4 cm resolution will be obtained if the maximal retardation is 0.25 cm; this is typical of the cheaper FTIR instruments. Much higher resolution can be obtained by increasing the maximal retardation. This is not easy,
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to measure the IR signal each time the laser signal passes through zero. Alternatively, the laser and IR signals can be measured synchronously at smaller intervals with the IR signal at points corresponding to the laser signal zero crossing being determined by interpolation. This approach allows the
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Deepty, M., Ch
Srinivas, E. Ranjith Kumar, N. Krisha Mohan, C. L. Prajapat, TV Chandrasekhar Rao, Sher Singh Meena, Amit Kumar Verma, and D. L. Sastry. "XRD, EDX, FTIR and ESR spectroscopic studies of co-precipitated Mn–substituted Zn–ferrite nanoparticles." Ceramics International 45, no. 6 (2019):
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The speed of FTIR allows spectra to be obtained from compounds as they are separated by a gas chromatograph. However this technique is little used compared to GC-MS (gas chromatography-mass spectrometry) which is more sensitive. The GC-IR method is particularly useful for identifying isomers, which
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The first FTIR spectrometers were developed for far-infrared range. The reason for this has to do with the mechanical tolerance needed for good optical performance, which is related to the wavelength of the light being used. For the relatively long wavelengths of the far infrared, ~10 μm tolerances
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An ideal beam-splitter transmits and reflects 50% of the incident radiation. However, as any material has a limited range of optical transmittance, several beam-splitters may be used interchangeably to cover a wide spectral range. For the mid-IR region the beamsplitter is usually made of KBr with a
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Commercial spectrometers use
Michelson interferometers with a variety of scanning mechanisms to generate the path difference. Common to all these arrangements is the need to ensure that the two beams recombine exactly as the system scans. The simplest systems have a plane mirror that moves linearly
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is the usual material for the near-IR, being both harder and less sensitive to moisture than KBr but cannot be used beyond about 8 μm (1,200 cm). In a simple
Michelson interferometer one beam passes twice through the beamsplitter but the other passes through only once. To correct for this an
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Systems where the path difference is generated by a rotary movement have proved very successful. One common system incorporates a pair of parallel mirrors in one beam that can be rotated to vary the path without displacing the returning beam. Another is the double pendulum design where the path in
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The interferogram is converted to a spectrum by
Fourier transformation. This requires it to be stored in digital form as a series of values at equal intervals of the path difference between the two beams. To measure the path difference a laser beam is sent through the interferometer, generating a
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The interferogram has to be measured from zero path difference to a maximum length that depends on the resolution required. In practice the scan can be on either side of zero resulting in a double-sided interferogram. Mechanical design limitations may mean that for the highest resolution the scan
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beam of light (a beam composed of only a single wavelength) at the sample, this technique shines a beam containing many frequencies of light at once and measures how much of that beam is absorbed by the sample. Next, the beam is modified to contain a different combination of frequencies, giving a
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atom into its two components by using his interferometer. A spectrometer with 0.001 cm resolution is now available commercially. The throughput advantage is important for high-resolution FTIR, as the monochromator in a dispersive instrument with the same resolution would have very narrow
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FTIR analysis is used to determine water content in fairly thin plastic and composite parts, more commonly in the laboratory setting. Such FTIR methods have long been used for plastics, and became extended for composite materials in 2018, when the method was introduced by
Krauklis, Gagani and
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it became possible to have a computer dedicated to controlling the spectrometer, collecting the data, doing the
Fourier transform and presenting the spectrum. This provided the impetus for the development of FTIR spectrometers for the rock-salt region. The problems of manufacturing ultra-high
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FTIR can be used in all applications where a dispersive spectrometer was used in the past (see external links). In addition, the improved sensitivity and speed have opened up new areas of application. Spectra can be measured in situations where very little energy reaches the detector aaurier
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The result of
Fourier transformation is a spectrum of the signal at a series of discrete wavelengths. The range of wavelengths that can be used in the calculation is limited by the separation of the data points in the interferogram. The shortest wavelength that can be recognized is twice the
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at all wavelengths, followed by series of "wiggles". The position of zero retardation is determined accurately by finding the point of maximum intensity in the interferogram. When a sample is present the background interferogram is modulated by the presence of absorption bands in the sample.
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the number of points in the interferogram has to equal a power of two. A string of zeroes may be added to the measured interferogram to achieve this. More zeroes may be added in a process called zero filling to improve the appearance of the final spectrum although there is no improvement in
638:. This is the spectral resolution in the sense that the value at one point is independent of the values at adjacent points. Most instruments can be operated at different resolutions by choosing different OPD's. Instruments for routine analyses typically have a best resolution of around
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Baker, Matthew J.; Trevisan, Júlio; Bassan, Paul; Bhargava, Rohit; Butler, Holly J.; Dorling, Konrad M.; Fielden, Peter R.; Fogarty, Simon W.; Fullwood, Nigel J.; Heys, Kelly A.; Hughes, Caryn; Lasch, Peter; Martin-Hirsch, Pierre L.; Obinaju, Blessing; Sockalingum, Ganesh D. (2014).
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were well-known, but considerable technical difficulties had to be overcome before a commercial instrument could be built. Also an electronic computer was needed to perform the required
Fourier transform, and this only became practicable with the advent of
938:. In modern FTIR systems the constant mirror velocity is not strictly required, as long as the laser fringes and the original interferogram are recorded simultaneously with higher sampling rate and then re-interpolated on a constant grid, as pioneered by
302:, which became available in 1965. Digilab pioneered the world's first commercial FTIR spectrometer (Model FTS-14) in 1969. Digilab FTIRs are now a part of Agilent technologies's molecular product line after Agilent acquired spectroscopy business from
212:
As mentioned, computer processing is required to turn the raw data (light absorption for each mirror position) into the desired result (light absorption for each wavelength). The processing required turns out to be a common algorithm called the
883:(ATR) is one accessory of FTIR spectrophotometer to measure surface properties of solid or thin film samples rather than their bulk properties. Generally, ATR has a penetration depth of around 1 or 2 micrometers depending on sample conditions.
736:
mirrors in place of the flat mirrors is helpful, as an outgoing ray from a corner-cube mirror is parallel to the incoming ray, regardless of the orientation of the mirror about axes perpendicular to the axis of the light beam. In 1966
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by their nature have identical masses. Liquid chromatography fractions are more difficult because of the solvent present. One notable exception is to measure chain branching as a function of molecular size in polyethylene using
414:. The form of the interferogram when no sample is present depends on factors such as the variation of source intensity and splitter efficiency with wavelength. This results in a maximum at zero retardation, when there is
205:—a certain configuration of mirrors, one of which is moved by a motor. As this mirror moves, each wavelength of light in the beam is periodically blocked, transmitted, blocked, transmitted, by the interferometer, due to
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that respond to changes in temperature as the intensity of IR radiation falling on them varies. The sensitive elements in these detectors are either deuterated triglycine sulfate (DTGS) or lithium tantalate
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198:
second data point. This process is rapidly repeated many times over a short time span. Afterwards, a computer takes all this data and works backward to infer what the absorption is at each wavelength.
694:. Alternatively, it allows a shorter scan-time for a given resolution. In practice multiple scans are often averaged, increasing the signal-to-noise ratio by the square root of the number of scans.
1674:"Structural, functional and magnetic ordering modifications in graphene oxide and graphite by 100 MeV gold ion irradiation". Vacuum. 182: 109700. 2020-12-01. doi:10.1016/j.vacuum.2020.109700
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Measuring the gas evolved as a material is heated allows qualitative identification of the species to complement the purely quantitative information provided by measuring the weight loss.
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The interferogram in practice consists of a set of intensities measured for discrete values of retardation. The difference between successive retardation values is constant. Thus, a
217:. The Fourier transform converts one domain (in this case displacement of the mirror in cm) into its inverse domain (wavenumbers in cm). The raw data is called an "interferogram".
861:
are sometimes used to extend the range to about 50 μm (200 cm). ZnSe is an alternative where moisture vapor can be a problem but is limited to about 20μm (500 cm). CaF
59:
of a solid, liquid, or gas. An FTIR spectrometer simultaneously collects high-resolution spectral data over a wide spectral range. This confers a significant advantage over a
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and allows for performing broadband spectroscopy on materials in ultra-small quantities (single viruses and protein complexes) and with 10 to 20 nm spatial resolution.
1914:
1738:
Amenabar, Iban; Poly, Simon; Nuansing, Wiwat; Hubrich, Elmar H.; Govyadinov, Alexander A.; Huth, Florian; Krutokhvostov, Roman; Zhang, Lianbing; Knez, Mato (2013-12-04).
182:, etc.) is to measure how much light a sample absorbs at each wavelength. The most straightforward way to do this, the "dispersive spectroscopy" technique, is to shine a
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FTIR spectrometers are mostly used for measurements in the mid and near IR regions. For the mid-IR region, 2−25 μm (5,000–400 cm), the most common source is a
209:. Different wavelengths are modulated at different rates, so that at each moment or mirror position the beam coming out of the interferometer has a different spectrum.
201:
The beam described above is generated by starting with a broadband light source—one containing the full spectrum of wavelengths to be measured. The light shines into a
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allows samples to be observed and spectra measured from regions as small as 5 microns across. Images can be generated by combining a microscope with linear or 2-D
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An FTIR interferogram. The central peak is at the ZPD position ("zero path difference" or zero retardation), where the maximal amount of light passes through the
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additional compensator plate of equal thickness is incorporated. Far-IR beamsplitters are mostly based on polymer films and cover a limited wavelength range.
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2010:
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are adequate, whereas for the rock-salt region tolerances have to be better than 1 μm. A typical instrument was the cube interferometer developed at the
257:), which becomes opaque at wavelengths longer than about 15 μm; this spectral region became known as the rock-salt region. Later instruments used
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50 μm (200 cm). The region beyond 50 μm (200 cm) became known as the far-infrared region; at very long wavelengths it merges into the
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range 4,000 cm to 660 cm). The lower wavelength limit was chosen to encompass the highest known vibration frequency due to a fundamental
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1480:"Investigating the impact of spectral data pre-processing to assess honey botanical origin through Fourier transform infrared spectroscopy (FTIR)"
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Echtermeyer. FTIR method uses the maxima of the absorbance band at about 5,200 cm−1 which correlates with the true water content in the material.
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for a given scan-time for observations limited by a fixed detector noise contribution (typically in the thermal infrared spectral region where a
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Brielle, Esther S.; Arkin, Isaiah T. (2018). "Site-Specific
Hydrogen Exchange in a Membrane Environment Analyzed by Infrared Spectroscopy".
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use of analog-to-digital converters that are more accurate and precise than converters that can be triggered, resulting in lower noise.
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people measure infrared absorption and emission spectra, i.e. why and how substances absorb and emit infrared light, see the article:
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410:(OPD). An interferogram is obtained by varying the retardation and recording the signal from the detector for various values of the
359:
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723:(FT) inverts the dimension, so the FT of the interferogram belongs in the reciprocal length dimension(), that is the dimension of
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sinusoidal signal where the separation between successive maxima is equal to the wavelength of the laser (typically a 633 nm
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to replace the prisms as dispersing elements, since salt crystals are opaque in this region. More sensitive detectors than the
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light beam at a sample, measure how much of the light is absorbed, and repeat for each different wavelength. (This is how some
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1969:
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Chamberain, J.; Gibbs, J.E.; Gebbie, H.E. (1969). "The determination of refractive index spectra by fourier spectrometry".
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germanium-based coating that makes it semi-reflective. KBr absorbs strongly at wavelengths beyond 25 μm (400 cm) so
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In practice, the accuracy is limited by the divergence of the beam in the interferometer which depends on the resolution.
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1248:"Agilent Technologies completes acquisition of Varian, Inc., marking historic milestone for two Silicon Valley pioneers"
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Tsagkaris, A. S.; Bechynska, K.; Ntakoulas, D. D.; Pasias, I. N.; Weller, P.; Proestos, C.; Hajslova, J. (2023-06-01).
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Connes, J.; Connes, P. (1966). "Near-Infrared Planetary Spectra by Fourier Spectroscopy. I. Instruments and Results".
674:. This arises from the fact that information from all wavelengths is collected simultaneously. It results in a higher
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921:. It used a stepper motor to drive the moving mirror, recording the detector response after each step was completed.
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The separation is the inverse of the maximum OPD. For example, a maximum OPD of 2 cm results in a separation of
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Scoble, Laura; Ussher, Simon J.; Fitzsimons, Mark F.; Ansell, Lauren; Craven, Matthew; Fyfe, Ralph M. (2024-02-01).
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Values of the interferogram at times corresponding to zero crossings of the laser signal are found by interpolation.
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1699:"Optimisation of classification methods to differentiate morphologically-similar pollen grains from FT-IR spectra"
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1805:"Near-Infrared Spectroscopic Method for Monitoring Water Content in Epoxy Resins and Fiber-Reinforced Composites"
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reduces the amplitude of any sidelobes and also the noise level at the expense of some reduction in resolution.
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of fundamental vibrations can be observed in this region. It is used mainly in industrial applications such as
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There are three principal advantages for an FT spectrometer compared to a scanning (dispersive) spectrometer.
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separation between these data points. For example, with one point per wavelength of a HeNe reference laser at
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Fourier-transform spectroscopy is a less intuitive way to obtain the same information. Rather than shining a
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1954:
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Smith, D.R.; Morgan, R.L.; Loewenstein, E.V. (1968). "Comparison of the Radiance of Far-Infrared Sources".
1088: – Type of Fourier transform in discrete mathematics − for computing periodicity in evenly spaced data
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in this region. Far-infrared spectrophotometers were cumbersome, slow and expensive. The advantages of the
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The spatial resolution of FTIR can be further improved below the micrometer scale by integrating it into
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The throughput or Jacquinot's advantage. This results from the fact that in a dispersive instrument, the
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Infracord produced in 1957. This instrument covered the wavelength range from 2.5 μm to 15 μm (
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1026:, examining the homogeneity of pharmaceutical tablets, and for differentiating morphologically-similar
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equivalent as the apparent wavelength is determined by the modulation frequency in the interferometer.
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The near-infrared region spans the wavelength range between the rock-salt region and the start of the
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Brault, James W. (1996). "New Approach to high-precision Fourier-transform spectrometer design".
1425:"Renal geology (quantitative renal stone analysis) by 'Fourier transform infrared spectroscopy'"
1059:, which is possible using chlorinated solvents that have no absorption in the area in question.
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resolution. Alternatively, interpolation after the Fourier transform gives a similar result.
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FTIR is a method of measuring infrared absorption and emission spectra. For a discussion of
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1094: – Mathematical transform that expresses a function of time as a function of frequency
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87:
1140:
1106: – Periodicity computation method − for computing periodicity in unevenly spaced data
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A quite different approach involves moving a wedge of an IR-transparent material such as
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84:(a mathematical process) is required to convert the raw data into the actual spectrum.
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detectors. The spatial resolution can approach 5 microns with tens of thousands of
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Interferometer schematics where the path difference is generated by a rotary motion.
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region. Measurements in the far infrared needed the development of accurately ruled
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adapted for FTIR, light from the polychromatic infrared source, approximately a
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cycles, respectively, in the interferogram. The corresponding frequencies are ν
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as the moving mirror must travel in a near-perfect straight line. The use of
1585:"Environment Polarity in Proteins Mapped Noninvasively by FTIR Spectroscopy"
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one arm of the interferometer increases as the path in the other decreases.
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1177:(Paperback ed.). New York: Oxford University Press. pp. 173–178.
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were required because of the low energy of the radiation. One such was the
1528:"Using Fourier transform IR spectroscopy to analyze biological materials"
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344: in this section. Unsourced material may be challenged and removed.
134: in this section. Unsourced material may be challenged and removed.
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Schematic diagram of a Michelson interferometer, configured for FTIR
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element heated to about 1,200 K (930 °C; 1,700 °F) (
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resolution elements, this increase is equal to the square root of
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1218:"Agilent Technologies to acquire Varian, Inc. for $ 1.5 Billion"
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Simple interferometer with a beam-splitter and compensator plate
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Manor, Joshua; Feldblum, Esther S.; Arkin, Isaiah T. (2012).
989:, chemistry, materials, botany and biology research fields.
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Krauklis, A. E.; Gagani, A. I.; Echtermeyer, A. T. (2018).
802:
FTIR setup. The sample is placed right before the detector.
281:. An additional issue is the need to exclude atmospheric
1100: – Spectroscopy based on time- or space-domain data
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TG-IR (thermogravimetric analysis-infrared spectrometry)
1175:
Principles of materials characterization and metrology
1071:
Water content determination in plastics and composites
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Nanoscale and spectroscopy below the diffraction limit
261:
prisms to extend the range to 25 μm (400 cm) and
27:
Technique to analyze the infrared spectrum of matter
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1993:
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719:The interferogram belongs in the length dimension.
245:. The upper limit was imposed by the fact that the
1880:Properties of many salt crystals and useful links.
452:runs to the maximum OPD on one side of zero only.
66:, which measures intensity over a narrow range of
30:"FTIR" redirects here. The term may also refer to
1873:Spectroscopy, part 2 by Dudley Williams, page 81
1133:Griffiths, P.; de Hasseth, J. A. (18 May 2007).
1042:platform. The corresponding technique is called
1198:"The Infracord double-beam spectrophotometer".
1686:https://doi.org/10.1016/j.ceramint.2019.01.029
741:measured the temperature of the atmosphere of
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1980:Vibrational spectroscopy of linear molecules
1371:Handbook of Vibrational Spectroscopy, Vol 1
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985:transform infrared spectroscopy is used in
180:ultraviolet-visible ("UV-vis") spectroscopy
91:An example of an FTIR spectrometer with an
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1975:Nuclear resonance vibrational spectroscopy
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1871:The Grubb-Parsons-NPL cube interferometer
757:himself attempted to resolve the hydrogen
447:Measuring and processing the interferogram
2348:Inelastic electron tunneling spectroscopy
2028:Resonance-enhanced multiphoton ionization
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1828:
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1714:
1634:The Journal of Physical Chemistry Letters
1608:
1589:The Journal of Physical Chemistry Letters
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1317:Journal of the Optical Society of America
997:FTIR is also used to investigate various
360:Learn how and when to remove this message
285:because water vapour has an intense pure
253:made from a single crystal of rock-salt (
150:Learn how and when to remove this message
2116:Extended X-ray absorption fine structure
1484:Journal of Food Composition and Analysis
1136:Fourier Transform Infrared Spectrometry
1116:
38:Fourier-transform infrared spectroscopy
18:Fourier Transform Infrared Spectroscopy
1040:scanning near-field optical microscopy
1703:Review of Palaeobotany and Palynology
7:
2421:
1429:International Urology and Nephrology
1168:
1166:
1164:
1162:
1160:
342:adding citations to reliable sources
132:adding citations to reliable sources
32:Frustrated total internal reflection
1369:Griffiths, P.R.; Holmes, C (2002).
489:) the shortest wavelength would be
44:) is a technique used to obtain an
1050:FTIR as detector in chromatography
827:Far-IR spectrometers commonly use
25:
2333:Deep-level transient spectroscopy
2085:Saturated absorption spectroscopy
2420:
2409:
2408:
2338:Dual-polarization interferometry
318:
108:
80:originates from the fact that a
2353:Scanning tunneling spectroscopy
2328:Circular dichroism spectroscopy
2323:Acoustic resonance spectroscopy
1224:. July 27, 2009. Archived from
1104:Least-squares spectral analysis
329:needs additional citations for
119:needs additional citations for
2282:Fourier-transform spectroscopy
1970:Vibrational circular dichroism
1716:10.1016/j.revpalbo.2023.105041
1098:Fourier-transform spectroscopy
684:generation-recombination noise
504:For a maximum path difference
460:is used). This can trigger an
1:
2080:Cavity ring-down spectroscopy
1985:Thermal infrared spectroscopy
1057:gel permeation chromatography
993:Nano and biological materials
964:region at about 750 nm.
2214:Inelastic neutron scattering
1410:10.1016/0020-0891(69)90023-2
1173:Krishnan, Kannan M. (2021).
881:Attenuated total reflectance
876:Attenuated total reflectance
870:Attenuated total reflectance
93:attenuated total reflectance
2275:Data collection, processing
2151:Photoelectron/photoemission
1884:University FTIR lab example
1646:10.1021/acs.jpclett.8b01675
1423:Singh, Iqbal (2008-09-01).
753:at 0.1 cm resolution.
747:vibration-rotation spectrum
462:analog-to-digital converter
2475:
2360:Photoacoustic spectroscopy
2302:Time-resolved spectroscopy
1496:10.1016/j.jfca.2023.105276
1086:Discrete Fourier transform
956:Near-infrared spectroscopy
953:
893:discrete Fourier transform
873:
371:
29:
2404:
2386:Astronomical spectroscopy
2365:Photothermal spectroscopy
1441:10.1007/s11255-007-9327-2
1252:Agilent Technologies, Inc
929:With the advent of cheap
899:(FFT) algorithm is used.
615:
416:constructive interference
686:). For a spectrum with
388:Michelson interferometer
374:Michelson interferometer
310:Michelson interferometer
291:Michelson interferometer
229:capable of recording an
203:Michelson interferometer
2370:Pump–probe spectroscopy
2259:Ferromagnetic resonance
2051:Laser-induced breakdown
1002:with the help of FTIR.
772:entrance and exit slits
408:optical path difference
176:absorption spectroscopy
100:Conceptual introduction
2449:Scientific instruments
2066:Glow-discharge optical
2046:Raman optical activity
1960:Rotational–vibrational
1866:Infracord spectrometer
1544:10.1038/nprot.2014.110
1356:10.1364/JOSA.58.000433
1329:10.1364/JOSA.56.000896
1006:Microscopy and imaging
897:fast Fourier transform
849:
829:pyroelectric detectors
803:
473:
431:
383:
171:
96:
2459:Infrared spectroscopy
2287:Hyperspectral imaging
1888:University of Bristol
1744:Nature Communications
847:
813:silicon carbide (SiC)
801:
788:Infrared spectroscopy
765:in the spectrum of a
676:signal-to-noise ratio
508:adjacent wavelengths
471:
429:
381:
165:
90:
77:infrared spectroscopy
2039:Coherent anti-Stokes
1994:UV–Vis–NIR "Optical"
1294:10.1364/AO.35.002891
672:Fellgett's advantage
338:improve this article
271:diffraction gratings
190:work, for example.)
188:UV–vis spectrometers
128:improve this article
2343:Hadron spectroscopy
2133:Conversion electron
2094:X-ray and Gamma ray
2001:Ultraviolet–visible
1821:2018Mate...11..586.
1756:2013NatCo...4.2890A
1402:1969InfPh...9..185C
1375:John Wiley and Sons
1286:1996ApOpt..35.2891B
1228:on January 13, 2017
729:spectral resolution
287:rotational spectrum
243:molecular vibration
225:The first low-cost
2391:Force spectroscopy
2316:Measured phenomena
2307:Video spectroscopy
2011:Cold vapour atomic
1878:Infrared materials
1830:10.3390/ma11040586
1764:10.1038/ncomms3890
850:
804:
474:
432:
398:and directed to a
384:
247:dispersing element
178:techniques (FTIR,
172:
97:
75:Fourier-transform
2436:
2435:
2400:
2399:
2292:Spectrophotometry
2219:Neutron spin echo
2193:Beta spectroscopy
2106:Energy-dispersive
1640:(14): 4059–4065.
1601:10.1021/jz300150v
1280:(16): 2891–2896.
1184:978-0-19-883025-2
1150:978-0-471-19404-0
1092:Fourier transform
936:helium–neon laser
887:Fourier transform
745:by recording the
721:Fourier transform
670:The multiplex or
655:rapid calculation
628:
627:
370:
369:
362:
259:potassium bromide
231:infrared spectrum
227:spectrophotometer
215:Fourier transform
207:wave interference
160:
159:
152:
82:Fourier transform
16:(Redirected from
2466:
2454:Fourier analysis
2424:
2423:
2412:
2411:
2272:
2183:phenomenological
1932:Vibrational (IR)
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1538:(8): 1771–1791.
1532:Nature Protocols
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1390:Infrared Physics
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1207:
1200:Clinical Science
1195:
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1154:
1139:(2nd ed.).
1130:
974:chemical imaging
917:and marketed by
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95:(ATR) attachment
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1950:Resonance Raman
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982:
970:process control
958:
952:
940:James W. Brault
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1860:External links
1858:
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1815:(4): 586–599.
1795:
1730:
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1595:(7): 939–944.
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1380:
1373:. Chichester:
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1274:Applied Optics
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954:Main article:
951:
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903:Spectral range
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950:Near-infrared
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919:Grubb Parsons
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739:Janine Connes
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699:monochromator
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327:This section
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117:This section
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2393:(a misnomer)
2379:Applications
2297:Time-stretch
2188:paramagnetic
2006:Fluorescence
1939:
1924:Spectroscopy
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1256:. Retrieved
1254:. 2010-05-14
1251:
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1230:. Retrieved
1226:the original
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1193:
1174:
1135:
1074:
1066:
1053:
1037:
1010:An infrared
1009:
996:
983:
980:Applications
959:
928:
925:Mid-infrared
911:
908:Far-infrared
890:
879:
851:
826:
810:
783:
781:
718:
709:
691:
687:
665:
652:
633:
503:
495:7900 cm
475:
454:
450:
437:
433:
421:
407:
403:
385:
356:
347:
336:Please help
331:verification
328:
283:water vapour
235:Perkin-Elmer
224:
211:
200:
192:
174:The goal of
173:
146:
137:
126:Please help
121:verification
118:
74:
72:
64:spectrometer
41:
37:
36:
1965:Vibrational
944:calibration
734:corner-cube
648:apodization
640:0.5 cm
636:0.5 cm
412:retardation
404:retardation
70:at a time.
68:wavelengths
2443:Categories
2171:Two-photon
2073:absorption
1955:Rotational
1868:photograph
1709:: 105041.
1684:8037-8044.
1490:: 105276.
1258:2023-11-04
1206:(2). 1957.
1111:References
1012:microscope
807:IR sources
794:Components
778:Motivation
725:wavenumber
715:Resolution
662:Advantages
611:= (n+1)/d
522:will have
458:HeNe laser
396:collimated
392:black-body
239:wavenumber
61:dispersive
53:absorption
2249:Terahertz
2230:Radiowave
2128:Mössbauer
1886:from the
1809:Materials
1772:2041-1723
1725:0034-6667
1552:1750-2799
1512:257530876
1504:0889-1575
1449:1573-2584
1044:nano-FTIR
966:Overtones
823:Detectors
755:Michelson
620:− ν
573:=d/(n+1)
350:June 2022
275:bolometer
267:microwave
140:June 2022
73:The term
2415:Category
2144:Electron
2111:Emission
2061:emission
2018:Vibronic
1849:29641451
1790:24301518
1750:: 2890.
1662:49621115
1654:29957958
1619:22563521
1570:24992094
1457:18228157
1302:21085438
1232:March 5,
1080:See also
1030:grains.
946:errors.
767:hydrogen
499:aliasing
487: cm
233:was the
57:emission
49:spectrum
46:infrared
2427:Commons
2254:ESR/EPR
2202:Nucleon
2030:(REMPI)
1840:5951470
1817:Bibcode
1781:3863900
1752:Bibcode
1610:3341589
1561:4480339
1465:2249696
1398:Bibcode
1282:Bibcode
1222:Agilent
987:geology
962:visible
221:History
2268:Others
2056:Atomic
1847:
1837:
1788:
1778:
1770:
1723:
1660:
1652:
1617:
1607:
1568:
1558:
1550:
1510:
1502:
1463:
1455:
1447:
1300:
1181:
1147:
1028:pollen
1020:pixels
832:(LiTaO
817:Globar
727:. The
624:= 1/d
548:d = nλ
304:Varian
249:was a
2209:Alpha
2178:Auger
2156:X-ray
2123:Gamma
2101:X-ray
2034:Raman
1945:Raman
1940:FT-IR
1658:S2CID
1508:S2CID
1461:S2CID
1016:array
859:KRS-5
743:Venus
607:and ν
604:= n/d
592:= 1/λ
588:and ν
582:= 1/λ
569:and λ
566:= d/n
534:and ν
528:(n+1)
386:In a
300:PDP-8
251:prism
1845:PMID
1786:PMID
1768:ISSN
1721:ISSN
1650:PMID
1615:PMID
1566:PMID
1548:ISSN
1500:ISSN
1453:PMID
1445:ISSN
1298:PMID
1234:2013
1179:ISBN
1145:ISBN
972:and
653:For
526:and
515:and
42:FTIR
2237:NMR
1835:PMC
1825:doi
1776:PMC
1760:doi
1711:doi
1707:321
1642:doi
1605:PMC
1597:doi
1556:PMC
1540:doi
1492:doi
1488:119
1437:doi
1406:doi
1352:doi
1325:doi
1290:doi
915:NPL
857:or
855:CsI
784:why
485:800
440:KBr
406:or
340:by
130:by
55:or
51:of
2445::
2242:2D
2161:UV
1843:.
1833:.
1823:.
1813:11
1811:.
1807:.
1784:.
1774:.
1766:.
1758:.
1746:.
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1346:.
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1319:.
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1276:.
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1220:.
1204:16
1202:.
1159:^
1143:.
1119:^
976:.
790:.
774:.
538::
483:15
306:.
1916:e
1909:t
1902:v
1851:.
1827::
1819::
1792:.
1762::
1754::
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1713::
1664:.
1644::
1638:9
1621:.
1599::
1593:3
1572:.
1542::
1536:9
1514:.
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1408::
1400::
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1292::
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1261:.
1236:.
1187:.
1153:.
863:2
834:3
761:α
759:H
751:2
692:m
688:m
622:1
618:2
616:ν
609:2
602:1
600:ν
594:2
590:2
584:1
580:1
578:ν
571:2
564:1
562:λ
556:2
550:1
536:2
532:1
524:n
519:2
517:λ
512:1
510:λ
506:d
493:(
481:(
363:)
357:(
352:)
348:(
334:.
153:)
147:(
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138:(
124:.
40:(
34:.
20:)
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