Introduction to Raman and Infrared Spectroscopy
Introduction to Raman and Infrared Spectroscopy
Aims
After course completion, the students will be able to:
- Understand the physics underlying the non-elastic scattering of light (Raman scattering) in molecules, solids, and low-dimensional systems (graphene and other two-dimensional crystals, quantum wells-wires-dots, electronic Raman scattering).;
- Understand the difference between Raman and (photo)luminescence spectroscopy;
- Understand the influence of stress and strain on the Raman spectra (Raman scattering by phonons);
- Have a good idea on the experimental aspects of Raman spectroscopy and understand the instrumentation used for it;
- Understand the physics of phonons;
- Understand the selection rules in Raman scattering.
Preliminary plan of the course
1) Classic description of Raman scattering by molecules. Raman and infrared active molecular vibrations (modes). Selection rules.
2) Physics of phonons - from chaotic movement of the atoms in a crystal due to temperature to a well-ordered description of this movement in terms of phonons. (A short introduction to lattice dynamics.)
3) Raman scattering in crystals. Classical description of Raman scattering by phonons.
4) Elements of Placzek’s polarizability theory.
5) Phonons as quantum oscillators and quantum description of the Raman effect. Temperature dependence of the Stokes - anti-Stokes parts if the spectrum.
6) Selection rules in Raman scattering by molecules and phonons - can we deal with them without group theory?
7) Equipment for laser and infrared spectroscopy.
8) Experimental part. Spectra of common substances (including crystals) will be measured and interpreted in terms of masses of the atoms involved in the vibrations (phonons) and forces between them. We shall bring up the role of the environment, too; e.g., why are the Raman spectra of solid crystals sharp but the liquids exhibit broad bands instead of sharp lines? How do the Raman spectra of gases look like? What is the difference between the Raman spectra of a (nearly) perfect crystal and an amorphous crystal of the same atom species?
9) Electronic Raman scattering.
10) Raman scattering from LO-phonon-plasmon coupled modes in semiconductors. Plasma frequency and relation to the doping concentration.
11) Fano resonance in heavily-doped semiconductors.
12) Resonant Raman scattering and its appearance in the Raman spectra.
13) Influence of stress/strain on the Raman spectra.
Examination
Problem solving during the course.
Written report on an individual project at the end of course.