IN THIS PRESENTATION I HAVE DISCUSSED ABOUT LASER RAMAN SPECTROSCOPY,ITS PRINCIPLE,WORKING, CONSTRUCTIO AND APPLICATIONS..

1. LASER RAMAN SPECTROSCOPY
WITH DIFFERENT EXCITATION
SOURCES
Presented By:-
PRAVEEN SONI
CSJMA18001390318

2. CONTENTS
1.WHAT IS SPECTROSCOPY?
2.WHAT IS SCATTERING OF LIGHT?
3.RAYLEIGH AND RAMAN SCATTERING
4.STOKES AND ANTI STOKES SCATTERING
5.INTRODUCTION TO RAMAN SPECTROSCOPY
6.PRINCIPLE OF RAMAN SPECTROSCOPY
7.SOURCES USED IN RAMAN SPECTROSCOPY
BEFORE LASERS AND THEIR DISADVANTAGES
8.ADVANTAGES OF LASER IN RAMAN
SPECTROSCOPY

3. 09.COMPONENTS OF LASER RAMAN SPECTROSCOPY
10.SCHEMATIC DIAGRAM OF RAMAN SPECTROSCOPY
11.THE SOURCE
12.SOME COMMON LASER USED IN RAMAN
SPECTROSCOPY
13.SAMPLE ILLUMINATION SYSTEM
14.SPECTROMETER
15.DETECTOR
16.DIFFERENCE BETWEEN RAMAN AND IR
SPECTROSCOPY
17.APPLICATIONS
18.REFERENCES

4. WHAT IS SPECTROSCOPY?
Spectroscopy is the study of the
interaction between matter and
electromagnetic radiation as a
function of the wavelength or
frequency of the radiation.
Spectroscopy is used as a tool for
studying the structures of atoms and
molecules.
The first spectroscope was invented
in 1814 by the physicist and lens
manufacturer Joseph Von
Fraunhofer .

5. WHAT IS SCATTERING
OF LIGHT?
When radiation passes
through a transparent
medium ,the species
present in that medium
scatter a fraction of
beam which is termed as
scattering of light.

6. RAYLEIGH AND RAMAN SCATTERING
Rayleigh Scattering
It is a elastic scattering phenomenon when radiation interacts with
matter.
In this type of scattering the energy of the scattered photons is
same as that of the incident photons after interacting with matter.
Raman Scattering
It is a inelastic scattering phenomenon when radiation interacts
with matter.
In this type of scattering the energy of the scattered photons is not
same as that of the incident photons after interacting with matter.

8. STOKES AND ANTI STOKES SCATTERING
Stokes Scattering
In this type of scattering the
frequency of the emitted
radiation is lower than the
incident radiation.
Anti Stokes Scattering
In this type of scattering the
frequency of the emitted
radiation is higher than the
incident radiation.

9. INTODUCTION TO RAMAN
SPECTROSCOPY
 Raman Spectroscopy was discovered by Chandrasekhara
Venkata Raman in 1928.
 Raman Spectroscopy is a spectroscopic technique mainly
used to observe vibration, rotational and other low frequency
modes in a system.
 Raman Spectroscopy is a popular technique because it is
non-destructive and in principles require no sample
preparation.
 This technique is commonly used in chemistry to provide a
fingerprint by which molecules can be identified.
 Raman Spectroscopy is the measurement of the wavelength
and intensity of inelastically scattered light from molecules.

10. PRINCIPLE OF RAMAN SPECTROSCOPY
 Monochromatic radiation is passed
through the sample such that the radiation
may get reflected, absorbed or scattered.
 The scattered have a different frequency
from the incident photon as the vibration
and rotational property vary.
 This results in the change of wavelength
which is studied in the IR spectra.
 The difference between the incident
photon and the scattered photon is known
as the Raman Shift.

11. SOURCES USED IN RAMAN
SPECTROSCOPY BEFORE LASERS AND
THEIR DISADVANTAGES
Commonly used sources before the invention of lasers were
435.8nm and 253.6nm emission lines of mercury lamps.
Disadvantages that occurs were:-
1.The source is an extended one and the brightness available per
unit area is very small.
2.The relative high frequency of mercury radiation often causes
the sample to fluorescence.
3.As coloured samples absorb in this high frequency region, it is
not possible to record their spectra.

12. ADVANTAGES OF LASER IN RAMAN
SPECTROSCOPY
 Excellent monochromaticity.
 Good beam focusing capabilities
and small line widths.
 The second order Raman spectra
could be recorded.
 The broadening due to doppler’s
effect could be minimized.

13. COMPONENTS OF LASER
RAMAN SPECTROSCOPY
The major
components in a
Laser Raman
Spectrometer are-
1. A source of
monochromatic radiation
2. Sample illumination
system
3. Spectrometer
4. Detection System
5. Computer

14. SCHEMATIC DIAGRAM OF RAMAN
SPECTROSCOPY

15. THE SOURCE
 Lasers are used as photons
sources due to their highly
monochromatic nature, and high
beam fluxes.
 The Helium-Neon Laser emits
highly monochromatic light at
632.8nm
 The Helium-Neon Laser is a
commonly used excitation source
used in the modern Raman
Spectrometers.

16. SOME COMMON LASER SOURCES
USED IN RAMAN SPECTROSCOPY

17. SAMPLE ILLUMINATION SYSTEM
Liquid Samples
Water is regarded as good solvents for the study of inorganic
compounds in Raman Spectroscopy because water is a weak
Raman scattered but a strong absorber of infrared radiation.
Solid Samples
Raman spectra of solid samples are often acquired by filling a
small cavity with the sample after it has been ground to a fine
powder.
Gas Samples
Gases are normally contained in glass tubes 1-2cm in diameter
and about 1mm thick. Gases can also be sealed in small
capillary tubes.

18. SPECTROMETER
 It disperses Raman Scattered light. A
polychromator with a diffraction grating is
typically used.
 It is used for recording or measuring
Raman spectra, especially as a method
of analysis.
 Now, Raman Spectrometer being
marketed are either Fourier transform
instruments equipped with cooled
germanium transducer or multichannel
instruments based upon charged coupled
device.

19. DETECTORS
 Detectors are used to detect the
signals obtained from the
spectrometer.
 Researchers traditionally used
single points detector such as
Photocounting or
Photomultiplier(PMT).
 Now a days Multichannel
detectors like Photodiode
Arrays(PDA) and Charged
Coupled Devices (CCD) are used
because they have very high
sensitivity and performance.

20. DIFFERENCE BETWEEN RAMAN AND IR
SPECTROSCOPY
RAMAN SPECTROSCOPY
 Water can be used as solvent.
 Accurate but not very sensitive.
 Optical system are made of quartz
and glass.
 It is due to the scattering of light by
the vibrating molecules.
IR SPECTROSCOPY
 Water cannot be used as solvent
because it is opaque to infrared
radiation.
 Accurate and very sensitive.
 Optical system are made of
special crystals such as CaF2
and NaBr etc..
 It is due to the absorption of light
by the vibrating molecules.

21. APPLICATIONS OF RAMAN
SPECTROSCOPY
 It is used to characterize materials, measure temperature and
find the crystallographic orientation of the samples.
 As a means to detect explosives for airport security.
 Used in medicine, aiming to the development of new drugs
and in the diagnosis of arteriosclerosis and cancer.
 Contaminant Identification.
 Pharmaceuticals and cosmetics.
 Provides a fingerprint by which molecule can be identified.

22. REFERENCES
BOOKS
1.R L LAKSH,(2004) INFRARED IN RAMAN SPECTROSCOPY,
RAJAT PUBLICATION.
2.M C TOBIN,(1996) LASER RAMAN SPECTROSCOPY,WILEY
PUBLICATION.
WEBSITES
https://www.horiba.com/ (FOR RAMAN SPECTROSCOPY
PRINCIPLE)
http://www.osa-opn.org/ (FOR RAMAN SCATTERING AND ITS
EFFECT)
https://www.ulsinc.com/ (FOR LASERS AND ITS ADVANTAGES)