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A UV-Vis spectrophotometer is an analytical instrument that measures the amount of ultraviolet (UV) and visible light that is absorbed by a sample. It is a widely used technique in chemistry, biochemistry, and other fields, to identify and quantify compounds in a variety of samples.
Ultraviolet-visible (UV-vis) spectroscopy involves energy levels that excite electronic transitions. Absorption of UV-vis light excites molecules that are in ground-states to their excited-states. [5] Visible region 400–700 nm spectrophotometry is used extensively in colorimetry science. It is a known fact that it operates best at the range ...
In modern spectrographs in the UV, visible, and near-IR spectral ranges, the spectrum is generally given in the form of photon number per unit wavelength (nm or μm), wavenumber (μm −1, cm −1), frequency (THz), or energy (eV), with the units indicated by the abscissa.
This avoids the problem of strong attenuation of the IR signal in highly absorbing media such as aqueous solutions. For ultraviolet or visible light (UV/Vis) the evanescent light path is sufficiently short such that interaction with the sample is decreased with wavelength. For optically dense samples, this may allow for measurements with UV.
Cary Model 14B Recording Spectrophotometer (front, details almost identical to Model 14) Cary Model 14 Recording Spectrophotometer (back, open) The Cary Model 14 UV-VIS Spectrophotometer was a double beam recording spectrophotometer designed to operate over the wide spectral range of ultraviolet, visible and near infrared wavelengths (UV/Vis/NIR).
[17]: 18 Its designation as a "UV–Vis" spectrophotometer indicates its ability to measure light in both the visible and ultraviolet spectra. [ 29 ] The DU was the first commercially viable scientific instrument for measuring the amount of ultraviolet light absorbed by a substance.
The restriction of the spin selection rule makes it even easier to predict the possible transitions and their relative intensity. Although they are qualitative, Tanabe–Sugano diagrams are very useful tools for analyzing UV-vis spectra: they are used to assign bands and calculate Dq values for ligand field splitting. [13] [14]
Ultraviolet–visible spectroscopy (UV–vis) can distinguish between enantiomers by showing a distinct Cotton effect for each isomer. UV–vis spectroscopy sees only chromophores, so other molecules must be prepared for analysis by chemical addition of a chromophore such as anthracene.