Quantum Theory of Raman Effect
Msc Chemistry Sem. 2nd
SEMINAR PRAJENTED BY DHARMENDRA
S.P.C. Government College Ajmer
2021-22

Content
 Introduction of Raman effect
 Quantum theory of Raman effect
 Reyleigh line
 Stokes line
 Anti stokes line
 Application of Raman effect

INTRODUCTION of Raman effect
 RAMAN EFFECT WAS FIRST DESCOVERD BY AN INDIAN
PHYSICIST SIR C.V.RAMAN IN 1928
 WHICH WAS AWARDED BY NABEL PRIZE IN PHYSICS IN
1930

Quantum Theory of Raman Effect
Accordin to quatum theory when a beam of monochromatic
light of freaqancy V0 in the from of photons each of energy
hV0 hits a molecule of a organic compound (like
benzin,toluine..etc) then following 3 things happene
E = hvo

Rayleigh Line
There can be elastic collision but ween incident photon and
molecule in this case these is no. exchange of energy but
ween incident photon and molecules so frequency of
scattered photon (v’) will be equal to frequency of
incident photon (Vo) which result in appearars of rayleigh
line in the scattered beam
E’=E
hv’=hVo
v’=Vo

Stokes line
 There can be in elastic collision but ween incident photon
and molecule in which the molecule might absorb part of
energy of incident photon as a resalt the frequency of
scattered photon (v’) will be less then the frequency of
incident photon (Vo) thise accounts for apperare of stokes
line in the scattered beam
E’< E
hV’< hVo
V’< Vo

Anti stokes line
There can be in elastic collision but ween incident photon
and molecule in which the molecule it self being in an
exuted stat imparts some of its energy to the incident phton
as a result the frequency scattered photon (V’) will be
greater than frequency of incident photon (Vo) this explains
the appearance of anti stokes line in the scattered beam
E’>E
hV’> hVo
v’>Vo

 Ep = energy of molecule before collision
 Eq = energy of molecule after collision
 Vo= frequency of incident photon
 V’= frequency of scattered photon
according to low of conservation of energy
Ep + hVo = Eq + hV’
Ep – Eq = hV’ – hVo
Ep – Eq = h(V’ – Vo)
Ep – Eq / h = V’- Vo

Vo + Ep –Eq / h = V’
1) Ep =Eq
V’= Vo (rayleigh line )
2) Ep<Eq
V’<Vo (stokes line)
3) Ep > Eq
V’ > Vo (anti stokes )

Application of Raman Effect
 In the study monitoring and quality assessment of
manufacturing processes of drugs petrochemicals and
cosmetics.
 In criminology the detection of specific substances (such
as narcotics) contained in packages or boxes without
opening them
 In the paint industry chemists can study what chemical
reactions take place in paint as it dries

Reference
* - https://youtu.be/VkrW8Gi16rY
* - Fundamental of molecular spectroscopy by P. S. Sindhu

Thank you……