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NIR absorption bands are typically 10–100 times weaker than the corresponding fundamental mid-IR absorption band.) [4] The lower absorption allows NIR radiation to penetrate much further into a sample than mid infrared radiation. Near-infrared spectroscopy is, therefore, not a particularly sensitive technique, but it can be very useful in ...
This radiation is absorbed by molecular vibrations, where the different atoms in a molecule vibrate around their equilibrium positions. This range is sometimes called the fingerprint region, since the mid-infrared absorption spectrum of a compound is very specific for that compound. Near-infrared, from 120 THz to 400 THz (2,500–750 nm ...
Infrared spectroscopy examines absorption and transmission of photons in the infrared range. [9] Infrared radiation is used in industrial, scientific, military, commercial, and medical applications. Night-vision devices using active near-infrared illumination allow people or animals to be observed without the observer being detected.
In the near-infrared range liquid water has absorption bands around 1950 nm (5128 cm −1), 1450 nm (6896 cm −1), 1200 nm (8333 cm −1) and 970 nm, (10300 cm −1). [ 19 ] [ 20 ] [ 15 ] The regions between these bands can be used in near-infrared spectroscopy to measure the spectra of aqueous solutions, with the advantage that glass is ...
Infrared radiation is divided into spectral subregions. While different subdivision schemes exist, [46] [47] the spectrum is commonly divided as near-infrared (0.75–1.4 μm), short-wavelength infrared (1.4–3 μm), mid-wavelength infrared (3–8 μm), long-wavelength infrared (8–15 μm) and far infrared (15–1000 μm). [48]
The near-infrared (NIR) window (also known as optical window or therapeutic window) defines the range of wavelengths from 650 to 1350 nanometre (nm) where light has its maximum depth of penetration in tissue. [1] Within the NIR window, scattering is the most dominant light-tissue interaction, and therefore the propagating light becomes diffused ...
There is no standard cut-off for the near-infrared range; therefore, the shortwave radiation range is also variously defined. It may be broadly defined to include all radiation with a wavelength of 0.1μm and 5.0μm or narrowly defined so as to include only radiation between 0.2μm and 3.0μm.
The infrared portion of the electromagnetic spectrum is usually divided into three regions; the near-, mid- and far-infrared, named for their relation to the visible spectrum. The higher-energy near-IR, approximately 14,000–4,000 cm −1 (0.7–2.5 μm wavelength) can excite overtone or combination modes of molecular vibrations.