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- What is it?
- Instrument Usage and
Features
- Applications
- Further
Information
1. What is it?
When light passes through a material,
some of it is absorbed and some of it is scattered. Nearly all of
the scattered light has identically the same frequency as the
incident light; this is called elastic scattering or Rayleigh
scattering. However, a tiny fraction of the scattered light is
shifted in frequency; this process is called Raman scattering and
the associated frequency shift is called the Raman shift. Raman
scattering is caused by the light interacting with some kind of
oscillation inside the material, and the Raman shift measures the
frequency of the oscillation involved. Many kinds of oscillations
produce Raman shifts, e.g. molecular vibrations and rotations,
lattice vibrations etc.; a complex structure like an organic
compound can oscillate in many ways and can therefore produce
a complicated Raman spectrum.
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2. Instrument Usage and Features
The Science Faculty possesses a
Jobin-Yvon
LabRam HR , which is located in the Department of Physics.
Samples are placed under the instrument's microscope and
illuminated by a focussed laser beam. Back-scattered light is
collected and analysed by a diffraction grating and CCD. A useful
spectrum from a single spot on the sample may be produced in
seconds. The automated scanning stage and temperature controller
permit fine scanning in 3 spatial coordinates and temperature.
- Wavelengths: 633nm (red), 514nm (green) and 488nm (blue)
- Raman shifts: 100cm-1 up to 3000cm-1 and
more.
- Resolution down to 0.35cm-1 (for the
1800mm-1 grating and red light).
- Scannable temperature range: -200°C to 600°C
- Automated XYZ mapping stage (0.1µm steps in X and Y)
3. Applications
Broadly, applications fall into
three categories:
- Analysis/mapping of chemical composition and contamination
- Analysis/mapping of strain
- Investigations of excitations in new materials and films
The following links to application
notes on the Jobin-Yvon website provide some indication of the sort
of studies that can be undertaken:
4. Further Information
The primary purpose of the machine is
to serve the needs of the research workers in the Science Faculty,
but providing specialist services to industry is also important,
and for this purpose the Raman service is affiliated to the
Loughborough Materials Characterisation Centre. For
further information contact:
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