And Its Application
Sakharkar Mohammad Anzar
Inorganic Chemistry (Paper-II)
Ramniranjan Jhunjhunwala College
• Mössbauer spectroscopy is a spectroscopic technique
based on the Mössbauer effect. This effect, discovered
by Rudolf Mössbauer in 1957, consists of the recoil-free,
resonant absorption and emission of gamma
rays in solids.
Fig: Recoil-free emission or absorption of a gamma-ray
when the nuclei are in a solid matrix such as a crystal
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• Just as a gun recoils when a bullet is fired, conservation of
momentum requires a free nucleus to recoil during emission
or absorption of a gamma ray.
• If a nucleus at rest emits a gamma ray, the energy of the
gamma ray is slightly less than the natural energy of the
transition, but in order for a nucleus at rest to absorb a
gamma ray, the gamma ray's energy must be slightly
greater than the natural energy, because in both cases energy
is lost to recoil.
• This means that nuclear resonance (emission and absorption of
the same gamma ray) is unobservable with free nuclei, because
the shift in energy is too great and the emission and
absorption spectra have no significant overlap.
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• Source :- Is mountain in solid metal overall weight is increased
and doppler bonding and required energy is minimize.
– The energy required by sample nuclei for γ- rays
absorption will depend on its chemical environment.
– The source nuclei should have half life atleast a few weeks.
• Collimator :- That filters out non-parallel gamma rays .
• Sample:- The solid sample are they contain operated solid
metal or crystal form.
• Detector :- G.M counter is used as detector; works on principle
of ionization of inert gas by high energy of γ-rays.
– Hence the current will be directly proportion al to γ-rays
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• 3 Types of Nuclear interactions that are
• Isomer (chemical, )shifts
• Quadrupole splitting
• Magnetic (hyperfine) splitting
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Isomer (Chemical, ) Shifts
Isomer shifts –
• Results from the electrostatic interaction between the
charge distribution of the nucleus and those electrons
which have a finite probability of being found around the
nucleus(only s electrons have a finite probability of
overlapping the nuclear density; can be influenced by p,d
electrons by screening the s density from nuclear
• Does not lead to splitting of energy levels but results in
a slight shift of Mossbauer energy levels in a compound
relative to the source
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Quadrupole splitting –
• The interaction of non-spherical or cubic extranuclear
electric fields with the nuclear charge density resulting
in splitting of the nuclear energy levels.
• For half-integral nuclear spins, the quadrupole
interaction results in I + ½ levels for spin I. For integral
nuclear spins, the degeneracy of the nuclear levels may
be completely removed by quadruple interaction to give
2I + 1 levels.
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Magnetic (hyperfine) splitting
Magnetic splitting –
• Is a result of the interaction between the nucleus and any
surrounding magnetic field.
• The nucleus spin I, splits into 2I+1 sublevels. The selection
rules mI= 0, 1 give rise to a symmetric 6-line spectrum.
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• To determine the oxidation state ‘Fe’ in it’s
– Higher the oxidation state mere is the construction of an ion
and more is the ‘S’ electron density within the nucleus with
lower the nuclear energy level and hence isomer shift is
ION Isomer Shift c/sec
Fe2+ 0.10 to +0.18
Fe3+ +0.04 to 0.09
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• To study the covalency in the metal-ligand bond
in the co-ordination compound:-
– If there is significant gap between M & L orbital and ‘L’
electrons one delocalized into metal orbital's then M-L
bonds is more covalent.
– This results in increasing electron density near the nucleus of
– Hence I.S value decreases. Thus covalency of M-L bond can be
– If the ligand is donor which is more electronegative then the
bond is less covalence & I.S value are high.
Compound I.S ()
K4Fe(CN) 6 0.008
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• To determine magnetic field in metallic
– The metallic ion have cubic geometry hence
quadrupole interactions is not expected but still we
get 6 lines spectra which can be assign magnetic
– The splitting of lines depend on the internal magnetic
field present in given species.
– This magnitude can be used to determine internal
magnetic field present in the given substance.
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• Gütlich, J.M.; The Principle of the Mössbauer Effect and Basic Concepts of
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