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Solid State Spectroscopy – Light Scattering1
Light Scattering
Deuterium
Solid State Spectroscopy – Light Scattering2
Solid State Spectroscopy – Light Scattering3
A bit of history
Inelastic Scattering of light was predicted theoretically in 1923 by A. Smekal
Experimental observation in 1928 by:
- C.V. Raman and K.S. Krishnan (Kalkutta)
- G. Landsberg and L. Mandelstam (Moscow)
Nobel Prize in 1930 for … C.V. Raman
A New Type of Secondary Radiation
C. V. RAMAN, K. S. KRISHNAN
Nature 121, 501-502 (31 March 1928)
A Change of Wave-length in Light Scattering
C. V. RAMAN
Nature 121, 619-619 (21 April 1928)
The Optical Analogue of the Compton Effect
C. V. RAMAN, K. S. KRISHNAN
Nature 121, 711-711 (5 May 1928)
Solid State Spectroscopy – Light Scattering4
Solid State Spectroscopy – Light Scattering5
Typical Raman spectra of high Tc superconductor
T.P. Devereaux & R. Hackl, RMP 79, 175 (2007)
Solid State Spectroscopy – Light Scattering6
Experiment
Solid State Spectroscopy – Light Scattering7
G1
G2
G3
s1
s2
s3
Polarizer(eI)
Analyzer (eS)
LASER
Raman Shift (cm-1)
Intensity
Sample
High resolution triple spectrometer
Solid State Spectroscopy – Light Scattering8
Experimental Techniques
Wavelength 104 Å 103 Å 102 Å 10 Å 0.1 Å
Energy 1 eV 10 eV 100 eV 1 keV 100 keV
Raman Scattering
Q ~0 Q ~ 1st BZ Q ~ several BZMax. Transfered Momentum
Soft x-rayRIXS
Hard x-rayIXS
Inelastic scattering of higher energy photon is a very different story !!!
Solid State Spectroscopy – Light Scattering9
Solid State Spectroscopy – Light Scattering10
kf
ki
Q
Θ
crystalline silicon (red), stressed silicon (yellow) and amorphous silicon (green). The blue areas correspond to a metal coating on the chip, which results in zero Raman signal.
www.horiba.com
Example : BaFe2As2
No BariumRaman mode
IR optic2A2u + 2Eu
Total Raman1A1g + 1B1g + 2Eg
Selection Rules
Incident and scattered photons polarization
Eg mode splitting ⇒ structural phase transition
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