U-V VISIBLE SPECTROSCOPY

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 U-V VISIBLE SPECTROSCOPY 

  • UV-Vis spectrum results from the interaction of EM radiation in the UV-Vis region with atoms and molecules.
  • The UV radiation region extends from 200nm to 400nm and the visible region extends from 500nm to 800nm.
  • Organic compounds, inorganic compounds, and coordination compounds fall in the UV-Vis spectrum.

THEORY

  • The absorption of radiation in the UV-Vis region of the spectrum is dependent on the electronic structure of the absorbing species. 
  • When a photon of a given wavelength interacts with a molecule it may cause a transition among the electronic energy levels if its energy matches with the difference in the energies of these levels.
  • A given electronic energy level has a number of vibrational energy levels in it and each of the vibrational energy levels has a number of rotational energy levels in it. So along with the electronic transition, vibrational and rotational transitions also occur simultaneously. So electronic spectrum appears broad.
  • Transitions involving π orbitals and lone pairs are identified using UV-Vis spectrometers.

INSTRUMENTATION 

  


The sample is irradiated with UV-Vis radiation from a source. Monochromatic radiation is employed at a time. The amount of radiation absorbed at each wavelength is measured.
Spectrum is the plot of wavelength or frequency versus intensity of absorption. 
Light absorbed is directly proportional to the concentration in the sample.
Location: United States

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