Mossbauer Spectroscopy

1. MOSSBAUER
SPECTROSCOPY
By-
Manish Sahu
M.Sc. Chemistry (Final)
Sp.- Physical Chemistry

2. SYNOPSIS :-
Introduction
History
Principle
Recoil energy
Mossbauer effect
Doppler effect
Formation of Mossbauer nuclides
Instrumentation and working
Mossbauer active elements
Applications
References
MOSSBAUER SPECTROSCOPY

3. INTRODUCTION :-
Mossbauer spectroscopy also known as nuclear gamma resonance
spectroscopy.
It is the study of gamma rays emission and subsequent re-absorption.
In Mossbauer spectroscopy nucleus absorbs the gamma ray photon
and undergo transition.

4. HISTORY :-
This type of phenomena was first observed by Rudolf Ludwig
Mossbauer in 1958 .
He received Nobel prize in 1961 .

5. BASIC PRINCIPLE:-
Consider radioactive 57CO which decays by electron capture to an excited state of
57Fe, which in turn decays to ground state emitting a gamma-ray of the appropriate
energy.it is called gamma fluorescence.
Another 57 Fe nucleus which is in ground state absorbs the gamma radiation and
become exited.
Gamma rey fluorescence
Gamma ray resonance
Electron capture

6. RECOIL ENERGY :-
A photon of high energy has relatively large mumentum.
Conservation of momentum requires a nucleus to recoil during emission or absorption of a
gamma ray.
Recoil energy is given by
Where, Egamma = is a energy of photon
M = mass of recoiled nuclei
c = valocity of light
Energy, which is used to recoil is called recoil energy.

7. MOSSBAUER EFFECT
For free nuclei this nuclear resonance is unobservable because in both case emission
and absorption of gamma rays, energy is lost to recoil, and shift in energy is too great.
If we bound the nucleus very strongly by keeping it in crystalline solid, than recoil
energy will be zero. Hence, recoil free Nuclear resources is observed.
This phenomena is known as Mossbauer effect.

8. DOPPLER EFFECT :-
If the emitting and Absorbing nuclei are in identical environment, the nuclear transition
energy would be equal, and absorption would be observed in rest position.
If the both nuclei are in different environment, the nuclear energy levels are shifted from
its original position. To bring the Nuclei in the resonance the energy of gamma ray Slightly
changed by Doppler effect
Doppler effect :- It is a change in frequencey of wave caused by th relative
motion between Wave source and The observer.

9. FORMATION OF MASSBAUER NUCLEI:-
The atoms in source emitting the gamma ray must be of same isotope as the atoms in the
sample absorbing them.
Suitable gamma ray source consists of a radioactive parent that decays to the desired
isotope.
Fe in exited state
(Mossbauer nuclei)

10. INSTRUMENTATION AND WORKING :-
Mossbauer spectrometer
Mossbauer spectrometer has three main parts :-
Sample :- Moves back and forth to generate Doppler effect
Collimator :- Filter out non- parallel Gamma ray .
Detector :- which detect transmittance.
When energy (in any particular velocity) is sufficient for the transition Of nuclei, it absorbs
the energy and we found a pic as a dip.

11. MOSSBAUER ACTIVE ELEMENTS :-
Most common elements studied are 57-Fe , 129-I , 119-Sn , 121-Sb
Mossbauer active elements are :-

12. APPLICATION OF MASSBAUER SPECTROSCOPY :-
Mossbauer spectroscopy is unique because it is very sensitive for small changes in
the chemical environment of the nucleus including oxidation state changes,
Magnetic Environment of sample.
As an analytical tool it is used in the field of geology for identifying the
composition of iron-containing specimens including meteors and moon rocks.
It is widely applied to Bioinorganic chemistry especially iron containing Proteins
and enzymes.

13. REFERENCE BOOK
Spectroscopy
BY Dr. H. Kaur
(Pragati prakasha)
E.M. McCASH
(MC Graw hill)
Fundamentals of molecular spectroscopy
BY Dr. C.N. Banwell