Vibrational Spectroscopy

“..everything that living things do can be understood in terms of the jigglings and wigglings of atoms..” [R. P. Feynmann, in "Six Easy Pieces" (Addison-Wesley, Reading MA), p. 59. (1991)]

This beamline is dedicated to vibrational spectroscopy, such as Infrared absorption and Raman scattering. These two experimental techniques allow to determine the vibrational properties of matter (phonons in solids or molecular vibrations, typically in the 100-5000 cm^-1 range) by analyzing its interaction with light: absorption and scattering of photons.

In Infrared spectroscopy, infrared light over a broad frequencies is passed through a sample. The matter absorbs the light only for some specific frequencies corresponding to the vibrational modes of the system and which fulfil some selection rules (the IR-active modes). Hence, for these frequencies, the light is attenuated when it passes through the sample. By measuring the intensity of the transmitted light at each frequency, the IR-active modes can be determined.

In Raman spectroscopy, a sample is illuminated with a monochromatic light (usually a laser beam in the visible, near infrared, or near ultraviolet range). The light interacts (inelastic or Raman scattering) with some specific vibrational modes of the system, which fulfil selection rules that are complementary to IR spectroscopy (Raman-active modes). As a result, the energy of the laser photons (and hence, the frequency of the light) may be shifted up or down by amounts corresponding to the various energies of the vibrational modes of the system.

What

• Infrared absorption: IR frequencies and intensities.
• Raman scattering: Raman frequencies and intensities.

Where

• Bulk, Surfaces and Nanostructures.

How

• Density Functional Perturbation Theory (DFPT).

Beamline Coordinator

Prof. Gian-Marco Rignanese

Université Catholique de Louvain, Louvain-la-Neuve, Belgium
gian-marco [dot] rignanese [at] uclouvain [dot] be

References

• Phonons and related crystal properties from density-functional perturbation theory,
  S. Baroni, S. de Gironcoli, A. Dal Corso, and P. Giannozzi, Rev. Mod. Phys. <>73, 515 (2001).
• Green-function approach to linear response in solids,
  S. Baroni, P. Giannozzi, and A. Testa, Phys. Rev. Lett. 58, 1861 (1987).
• Density-functional approach to nonlinear-response coefficients of solids,
  X. Gonze and J.-P. Vigneron, Phys. Rev. B 39, 13120 (1989).
• Dynamical matrices, born effective charges, dielectric permittivity tensors, and interatomic force constants from density-functional perturbation theory,
  X. Gonze and C. Lee, Phys. Rev. B 55, 10355 (1997).
• Nonlinear optical susceptibilities, raman efficiencies, and electro-optic tensors from first-principles density functional perturbation theory,
  M. Veithen, X. Gonze, and Ph. Ghosez, Phys. Rev. B 71, 125107 (1997).
• First-principle studies of the lattice dynamics of crystals, and related properties,
  X. Gonze, G.-M. Rignanese, and R. Caracas, Z. Krist 220, 458 (2005).