Introduction of Raman spectroscopy

1. Group 5th
- Ahzab Sandi
- Wilson Jefriyanto
RAMAN SPECTROSCOPY
Presented on:
The lectures of Analytical Instruments

2. Outline
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3. Introduction
ELECTROMAGNETIC
RADIATION OF
INFRARED
IR ABSORBTION
SPEKTRODCOPY
RAMAN SPECTROSCOPY
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4. Theory of Raman Spectroscopy 4
• In 1928, Sir C.V. Raman documented the phenome
non of inelastic light scattering
• The scattering of light at the same as frequency
incident radiation is called Reyleight scattering
• However a small difraction of the scattered light
is observed to have different frequency from that
of irradiating light. This is known as the Raman
scattering
• An Interaction the incident photons and the vibrat
ional energy levels of the mocular.
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hni
h(ni-nR)
hni
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S0
Energy
Virtual Level
Rayleigh Raman (inelastic)
(elastic) Scattering Scattering

5. Stokes and Anti-Stokes
• Radiation is often characterized by its
wavelength (λ)
• In spectroscopy, because we are interested
in the interaction of radiation with states
• molecule being examined and this being
usually discussed in terms of energy
• useful to use frequency (n) or wavenumber
(v) scales, which are linearly related with
energy
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• The transition occurring below
the Rayleight or exciting line are
Stokes lines (V1 + ΔV)
• Those above it are called anti-
stokes (V1 - ΔV)

6. Video
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7. The major components in a Raman system are:
 A source of monochromatic radiation
 Sample compartment and associated optics
 Spectrometer or monochrometer
 Detection system
 Computer
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Component of Instrument 7

8. Scheme for Raman Spectroscopy
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9. The Source
• Laser are used as photon sources due to their highly
monochromatic nature, and high beam fluxes.
• The helium-neon laser, which emits highly monochrom
atic light at 632.8 nm,
• The helium-neon laser, is a commonly used excitation
source in the modern Raman spectrometers.
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10. Sample
• In Raman spectrometers, samples may be examined as
solids, liquids or solutions, or in the gas phase.
• Raman spectrum is most easily obtained by using liquid
samples.
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11. The Spectrometer
• It was explained that the intensity of Raman lines much
weaker than the exciting line.
• One of the great challenges in Raman spectroscopy is t
o remove the Rayleigh signal. This is accomplished in th
e old spectrometers by using very large double or triple
monochromators with large focal lengths (up to 1 m) a
nd very high resolution
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12. The Detector
• The most commonly used detector is the photomultiplier tube
which provides excellent sensitivity, low noise and a large dy
namic range.
• A multi–channel detector may be a one-dimensional diode
array, with 512 or 1024 pixels or a two-dimensional type like
vidicon or charge coupled devices
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13. Computer
• Computers incorporated in the modern instruments are essential
for manipulation (addition, substraction, self-deconvolution, etc)
• They are indispensable when a multi-channel detector is being u
sed and offer a major advantage with a single channel system.
• good Software and graphics facilities for Raman spectroscopy is
a rapidly developing analytical tool.
• several new advanced techniques are being developed, with a
view to enhance the utility.
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14. • Lattice vibrations in ammonium perrhenate
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15. Application
• Raman spectroscopy is commonly used
in chemistry, since vibrational informati-
on is specific to the chemical bonds
and symmetry of molecules.
• Therefore, it provides a fingerprint by
which the molecule can be identified.
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 In solid-state physics, spontaneous
Raman spectroscopy is used to,
characterize materials, measure
temperature, and find the
crystallographic orientation of a
sample

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