Labor Campus Golm
When electromagnetic radiation irradiates a molecule, it may be transmitted, absorbed or scattered.
While the Tyndall effect describes scattering by microscopic particles (e.g. smoke or fog). In Rayleigh scattering, molecules themselves scatter light (one result is the blue sky). Both effects do not change the wavelength of the scattered light.
Careful inspection however reveals that in addition to the Rayleigh scatter at the incident wavelength, a tiny proportion is shifted to longer wavelengths. This shifted radiation was experimentally observed in liquids and first published in March 1928 by Raman & Krishnan. Almost simultaneously, soviet physicists Landsberg & Mandelstam observed the same effect in crystals. The phenomenon was named after the Indian physicist Chandrasekhara Venkata Raman, who was awarded The Nobel Prize in Physics in 1930 “for his work on the scattering of light and for the discovery of the effect named after him”.
In this lab course, the basic features of Raman scattering will be investigated using different spectrometers and techniques.
- measurement of a weakly fluorescent sample with a luminescence spectrometer
- assignment of all observed features, justification of these assignments
- wavenumber calibration of a Raman spectrometer, using a reference material
- measurement of Raman spectra for different samples
- assignment of the observed features to molecular properties
- material identification with the help of Raman spectra
- relation of features observed in the luminescence spectra to features observed in Raman spectra of the same compounds