electron X-ray and neutron diffraction

1. DEPARTMENT OF PHYSICS
INDIAN INSTITUTE OF TECHNOLOGY ,GUWAHATI
By BHOLU RAM SWAMI
GUIDED : DR.D PAMU

2.  Introduction :
 Diffraction
 X-ray Diffraction
 Electron Diffraction
 Neutron Diffraction
 Basic Difference b/w x-ray
,electron and neutron diffraction
 Advantages

3. Introduction
Diffraction : : The process by which a beam of
light or other system of waves is spread out as
result of passing through a narrow aperture or
across an edge.

4. X-ray diffraction : The atomic planes of a crystal
cause an incident beam of X-rays to interfere with one
another as they leave the crystal. The phenomenon is
called X-ray diffraction.
Electron diffraction: the diffraction of a
beam of electrons by atoms or molecules,
used especially for determining crystal
structures.
Neutron diffraction : Neutron diffraction or
elastic neutron scattering is the
application of neutron scattering to the
determination of the atomic and/or
magnetic structure of a material

6. Discovery of electron diffraction

7. X –ray diffraction Electron diffraction Neutron diffraction
Wavelength needed for
crystal diffraction of the
order of λ=1Å which is
same size as an atom
Wavelength needed for
crystal diffraction of the
order of λ=1Å
Wavelength needed for
crystal diffraction of the
order of λ=2Å
X-ray have energy
E=10^4 e V
Electrons have the
energy
E ̴ 40 e V
Neutrons have the
energy
E ̴ 0.08 e V

8. Graph between wavelength Vs energy

9. Atomic scattering power
decreases as scattering
angle increase.
X-ray scattering
amplitude is strongly
dependent on sin q/l
making it very difficult
to get good quality x-ray
data at high sin q/l
Atomic scattering power
Decreases as increases
angle .
Atomic scattering power
is change erratically with
angle .

10. X-ray diffraction Electron diffraction Neutron diffraction
 X-ray is the cheapest
the most convenient and
widely used method.
Electron beam can easily
produced by cathode
tube ,easily available .
 Neutron sources in the
world are limited so
neutron diffraction is a
very special tool and
very expensive.
 X-rays interact with
the spatial distribution of
the valence electrons.
electrons are charged
particles and interact
with matter through
the Coulomb forces. This
means that the incident
electrons feel the
influence of both the
positively charged
atomic nuclei
 neutrons are scattered
by the atomic nuclei
through the strong
nuclear forces. In
addition, the magnetic
moment of neutrons is
non-zero, and they are
therefore also scattered
by magnetic fields

12. X-ray diffraction Electron diffraction Neutron diffraction
Normal penetration Less penetration Highly penetration
X-rays and electrons are scattered by atomic electrons
whereas neutrons are scattered by atomic nuclei. This results in
a number of differences, perhaps the most important being in
the scattering from light elements. Whereas one electron on a
hydrogen atom can be hard to find by X-ray or electron
diffraction, the hydrogen nucleus scatters neutrons strongly
and is easily found in a neutron diffraction experiment.
The magnetic structure of materials is determined by neutron
diffraction ,electron and x-ray diffraction doesn’t give any
inform about magnetic property .
To measure the thickness of thin films and multi-layers we use
only electron diffraction ,x-ray and neutron diffraction can’t.

13. Range of diffraction

14.  Measurement under atomsphere pressure
 XRD is Non destructive technique ,easly sample
perp.
 X-ray are not observed very much by air, so the
speciman need not be in evacuated chamber
 Probe depth controle by incidence angle
 X-ray diffraction structure analysis can be applied
for single crystal
 All structure information is in reciprocal space we
collect and measure HKL intensities ,then solve
and refine a crystal structure

15.  Crystal cell symmetry ,cell parameters can be
easily extracted from electron diffraction
patterns
 Diffracted beam have high intensity.
 Can handle nano -size crystals.
 Small amount of material needed.

16.  Crystals do not absorb neutrons ,so they are
useful for studying components that contain
heavy atoms that strongly absorb x-rays
 Neutrons can penetrate several millimeters of
materials like aluminium and steel
 Neutrons are more useful than X-rays for
determining the crystal structures of solids
containing light elements i.e. Neutrons
interact very strongly with lighter elements.

17. Thank you