Nuclear magnetic resonance spectroscopy is a powerful technique for chemical analysis that involves the absorption of radiofrequency radiation by atomic nuclei in a magnetic field. It is useful for determining molecular structures and understanding how molecules function. The technique works by exciting atomic nuclei to higher energy states using radiofrequency pulses in a strong magnetic field. As the nuclei relax back to lower energy states, they emit radiofrequency signals that can be analyzed to provide information about molecular structure. NMR spectroscopy is widely used across many fields due to its applicability to a variety of sample sizes.

1. -- PRIYASRIVASTAVA
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EIE, VI SEM.

2. BASIC:
For mapping It is recognized as
molecular one of the most
Nuclear Magnetic
structures & powerful
Resonance
learning how techniques for
spectroscopy is a
molecules chemical
NDT.
function & relate
analysis.
to each other.

3. The study of absorption
of radiofrequency
radiation by nuclei in a
magnetic field is called
Nuclear Magnetic
Resonance.

4. UTILITIES & IMPORTANCE
The importance of this The utility of this is for structural
technique is reflected in the characterization arises because
efforts that have been made to different atoms in a molecule
extent its applicability to smaller experience slightly different
& smaller sample sizes. magnetic fields.

5. PRINCIPLES
The angular
Nuclear
momentum
associated with
the spin of the
particle would be Spin
an integral or a
half-integral
multiple of h/2pi.
Elementary particles such
as electrons or a nucleus
are known to behave as if
they rotate about an axis
& thus have the property
of spin.

6. Nuclear Energy
Levels
Since a nucleus possesses
a charge, its spin gives rise
to a magnetic field that is
analogous to the field
produced when an electric
current is passed through
a coil of wire.
When a spinning nucleus
is placed in a strong
uniform magnetic field(H),
the field exerts a torque
upon the nuclear magnet.

7. Resonance
Conditions
When an alternating radiofrequency
field, superimposed over the stationary
In general, the energy difference magnetic field, rotates at exactly the
frequency of an energy level, the nuclei
b/w states is given by: will be provided enough energy to
undergo a transition from a lower
energy level to a higher energy level.

8. RELAXATION PROCESS
When nuclei in the higher energy However, the emission is
state return to the lower state, insignificant because the
emission of radiation takes place. probability of re-emission of
There are two major R.P- photons varies with the cube of
the frequency. At radio-
1.Spin-lattice(longitudinal)
frequencies, re-emission is
2.Spin-Spin(transverse) negligible.

9. It is expressed The Chemical
as: shift
The difference b/w
the field necessary
for resonance in
the sample & in
some arbitrarily
chosen reference
compound is
called the
‘Chemical Shift’.

10. TYPES
Continuous-Wave NMR Spectroscopy
A CW-NMR spectrometer consists of a control console,
magnet, & two orthogonal coils of wire that serve as
antennas for radiofrequency radiation.
One coil is attached to an rf generator & serves as a
transmitter.
The other coil is the rf pick-up coil & is attached to the
detection electronics.

11. Fourier Transform NMR Spectroscopy
It use a pulse of rf radiaiton which causes nuclei in
a magnetic field to flip into the higher energy
alignment.
Due to Heisenberg uncertainty principle, the
frequency width of the rf pulse is wide enough to
simultaneously excite nuclei in environment.
All the nuclei will re-emit rf radiation at their
respective resonance frequencies, creating an
interference pattern in the resulting rf emission
vs. time, known as FID(Free Induction Decay)

12. CONSTRUCTIONAL DETAILS

13. The key parts of the system are:-
A magnet which produces a magneitc field
in the range 10,000-25,000 gauss,
Radio-frequency transmitting
system,
The signal amplifier &
detector,
A display device,
A non-magnetic
sample holder
Computer
workstation

14. ELECTRON SPIN RESONANCE
SPECTROMETERS
It involves detecting the
detection of a physical It is the study of magnetic
phenomenon of dipoles of electronic
absorption of origin by applying, usually
electromagnetic radiation fixed microwave
in the microwave region frequencies to a sample
by paramagnetic species residing in a varying
that are subjected to an magnetic field.
external magnetic field.

15. DETAILED DESCRIPTION OF ESR
SPECTROMRTER

16. INSTRUMENTATION FOR E.S
A source of radiation
with which to excite
the sample.
An electron energy
analyzer,
It contains the
following An electron detector
components:
A read-out system,
&
A high vacuum
system

17. INSTRUMENTATION FOR X-RAY
SPECTROMETRY
THE IMPORTANT
PARTS ARE:-
X-ray generating
equipment,
Collimator,
Monochromators,
and
Detectors