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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 schematic representation of a nano-FTIR system with a broadband infrared source. Nano-FTIR (nanoscale Fourier transform infrared spectroscopy) is a scanning probe technique that utilizes as a combination of two techniques: Fourier transform infrared spectroscopy (FTIR) and scattering-type scanning near-field optical microscopy (s-SNOM).
[1] [2] In physical and analytical chemistry, infrared spectroscopy (IR spectroscopy) is a technique used to identify chemical compounds based on the way infrared radiation is absorbed by the compound. The absorptions in this range do not apply only to bonds in organic molecules.
Without the slit used in dispersive spectroscopy, FTIR allows more light to enter the spectrometer and gives a higher signal-to-noise ratio, i.e. a less-disturbed signal. [8] The IR laser used has a known wavelength and the velocity of the movable mirror can be controlled accordingly.
Two-dimensional infrared spectroscopy (2D IR) is a nonlinear infrared spectroscopy technique that has the ability to correlate vibrational modes in condensed-phase systems. This technique provides information beyond linear infrared spectra, by spreading the vibrational information along multiple axes, yielding a frequency correlation spectrum.
An ATR accessory for IR spectroscopy. ATR uses a property of total internal reflection resulting in an evanescent wave. A beam of infrared light is passed through the ATR crystal in such a way that it reflects at least once off the internal surface in contact with the sample. This reflection forms the evanescent wave which extends into the sample.
The particle size should be smaller than the wavelength of the incident light in order to minimize Mie scattering, so this would infer that it should be less than 5 μm for mid-infrared spectroscopy. The spectra are plotted in units of log inverse reflectance (log 1/R) versus wavenumber.
The method of Fourier-transform spectroscopy can also be used for absorption spectroscopy. The primary example is " FTIR Spectroscopy ", a common technique in chemistry. In general, the goal of absorption spectroscopy is to measure how well a sample absorbs or transmits light at each different wavelength.