Ultraviolet-visible (UV-Vis) Spectroscopy

Asst. Lect. Anhar Abd Alsalam Oda
alfahdawi2@uoanbar.edu.iq

 Known as "UV" for short, ultraviolet light has a wavelength between 10 and 400 nm (30 pHz and 750 THz). This spectrum is thought to extend further than X-rays but to be shorter than visible light. UV rays found in sunlight account for over 10% of the sun's total electromagnetic energy output. This form of electromagnetic radiation is also produced by electric arcs and certain types of lights, including black light, tanning lamps, and mercury-vapor lamps. Due to the absence of proton energy, which is required for atom ionization, long-wavelength UV is not considered ionizing radiation. However, the long-wavelength UV may cause a chemical reaction, which in turn causes numerous compounds to glow or fluoresce. The biological and chemical effects of UV radiation are, therefore, expected to be significantly greater than those of mere heating.

At the same time, the electromagnetic radiation that can be directly seen by humans is referred to as the visible light (Vis) spectrum. The visible spectrum extends from 380 to 740 nm in wavelength, which is a sweet spot for human vision. With regards to frequency, the Vis spectrum covers the range from 405.8 to 790 THz. Not all visible hues are included in this particular spectrum's generation. As a result, it is extremely difficult to achieve magenta or pink without resorting to extensive wavelength mixing. Pure colors, or those with only one wavelength, are referred to as spectral colors.

Transmission, reflection, and absorption spectra of a substance in liquid and solid form can be acquired through the use of ultraviolet-visible (UV-Vis) light spectroscopy, which is a strong analytical depiction. Electrons in the ground state are excited to the first excited state of the chemical, and this can be seen by measuring the absorbance, transmission, and reflectance of electromagnetic radiation and light energy using spectroscopy.

The ultraviolet-visible (UV-Vis) portion of the electromagnetic spectrum spans from about 200 to 800 nm in wavelength (1.5 to 6.2 eV in energy). Absorbance/transmittance/reflectance spectroscopy is based on the Beer-Lambert Law, as shown by Equation.

A single wavelength absorbance (which is a unitless quantity typically observed in arb/arbitrary units) is denoted by the symbol A. While a molecule or compound in solution is represented as M^-1cm^-1, the letters b and c denote the path length of the sample holder and the concentration of the solution, respectively.

      UV-vis spectroscopy data could give both numerical and qualitative insight into a certain molecule or substance. It is critical to apply a zero reference cell regardless of the kind of information required, be it qualitative or quantitative.