Quantum Theory of Raman effect

Dharmendra semester 2

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

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

3. 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

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

5. 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

6. 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

7. 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

8. 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

9. 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 )

10. 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

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

12. Thank you… …