Excitation of molecules

Principle

The position of the longest wavelength π - π* -absorption band in the UV-visible spectrum of organic compounds which have chromophoric systems can be approximately calculated by various methods. For dyes with extended conjugated π-systems, the model of the electron in an unidimensional potential box (confinement region) supplies results that agree sufficiently well with experimental results.

Tasks

1. Plot the absorption spectrum of carotene, a polyene dye, in the visible range of electromagnetic radiation.
2. Compare the wavelength of the absorption maximum determined from this with the value calculated from the representation of the elctron in a unidimensional box
3. Discuss this comparison.

What you can learn about

• Wave mechanics atomic model
• Model of electrons in a unidimensional potential box
• Ground and excitation states of molecules
• Electron excitation spectroscopy (UV-visible spectrometry)
• Spectroscopical energy and adsorption measurement
• Chemical theory of colour
• Lambert-Beer's Law
• Photometry
• Chromatography

Literature for this article als follows

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