Vlasta Mohaček Grošev Training School on Raman Spectroscopy, COST Action MP 1302 “Nanospectroscopy”, Zagreb

differing types of molecules have differing absorptions of infrared radiation because their molecular structures give them differing oscillating resonances book “Heat Considered as a Mode of Motion” I ∝ ω 4

used Maxwell’s theory of radiation to explain plasmon resonances in colloid suspensions of metal particles scattering on particles d ≳ λ

Tcherniak et al.: Probing a Century Old Prediction One Plasmonic Particle at a Time. Nano Letters 10 (4) (2010) 1398–1404.

John William Strutt, 3rd Baron Rayleigh scattering on particles d << λ I ∝ ω 4

searched for “optical analogue of the Compton effect” met Compton at a meeting of British Association in Toronto performed measurements on liquids usig focused sunlight On 7th July published the article in Nature with K. S. Krishnan in which explicitly they attributed the newly found spectral lines to molecular vibrations. K. S. Krishnan

NOBEL PRIZE FOR PHYSICS FOR WENT TO RAMAN.

laser light: h ν 0 scattered light: h ν wavenumber is defined as 1/ λ measured in cm -1

H. J. Galla, Spectroscopische Methoden in der Biochemie, Georg Thieme Verlag 1988.

Intensity of the oscillating dipole p 0 ν S frequency of the dipole oscillation is the wavenumber of the oscillations

linear Raman effect

Time dependent wave functions of the initial and final states are approximated with the unperturbed functions and corrections:

H. J. Galla, Spectroscopische Methoden in der Biochemie, Georg Thieme Verlag 1988.

ω fi = ω f – ω i < 0 ω fi = ω f – ω i = 0 ω fi = ω f – ω i > 0

The selection rules for the i ⤍ f transition require that both the and the be different from zero. symmetry of the tensor α ρσ is given for each point group symmetry of Q k and the nature of Q k one finds via normal coordinate analysis

ξ represents all nuclear coordinates x represents all electronic coordinates

From Pauling&Wilson: “Introduction to Quantum Mechanics”, Dover Full line - probability density of finding a particle in the oscillator quantum state with n =1 (left) and n = 10 (right). Dashed line – classical probability.

in such a way so that kinetic and potential energy have DIAGONAL form: Normal coordinates Q k are defined as Atoms vibrate in normal modes in such a way that each atom reaches maximum amplitude at the same time.

gauche C 2 trans C 2h

Technische Universitaet Darmstadt, dr.Stefan Immel Tutorials Symmetry Point groups

(COOH) 2 oxalic acid tTt conformer V. Mohaček Grošev et al. J. Raman Spectrosc. J. Raman Spectrosc. 2009, 40, 1605–1614.

Γ vib = 7 A g + 2 B g + 3 A u + 6 B u

A g and B g modes are RAMAN active

Vibrations are calculated numerically, e.g. via Gaussian.

Removing the acoustic modes

Matrix of the polarisability tensor in the crystal has components of A g and B g symmetry. Symmetry elements are now CRYSTAL SYMMETRY elements.

XXI International Conference on Horizons in Hydrogen Bond Research T64000 HORIBA Jobin Yvon Raman spectrometer nm (green) laser line CCS 350 Janis Research cryostat

XXI International Conference on Horizons in Hydrogen Bond Research single crystal was placed in the capillary and mounted inside the cryostat figure by K. Furić, V. Volovšek: J. Mol. Struct. 976 (2010) 174–180.

Spectra of powder sample exhibit the same behaviour found in z(yy)x +z(yz)x spectra:

z(yy)x + z(yz)x Low frequency Raman spectra do not show any change that would indicate phase change:

However, when the polarization of the electric field is along a crystal axis (here z), significant increase of hydrogen bond modes is observed: