X-ray Diffraction (XRD)
X-rays production process
example
1) An electron in the K shell is ejected from the
atom by an external electron
X-rays production process
example
2)An electron from the L or M shell "jumps in“
to fill the vacancy. In the process,
it emits a characteristic x-ray
unique to this element and in turn,
produces a vacancy in the L or M shell.
Production of X-rays
Typical XRD Machine
Basic Features of Typical XRD
Experiment
What is X-ray Diffraction
� Bragg’s Law � certain angles of
incidence (theta ).
� The variable d is the
distance between atomic
layers in a crystal,
� and the variable λis the
wavelength of the
incident X-ray beam;
� n is an integer.
Constructive and Destructive
Interference of Waves
Deriving Bragg’s Law
How waves reveal the atomic structure of crystals
This observation is an
example of X-ray wave interference
It was direct evidence for the
periodic atomic structure of
crystals
Example of an X-ray powder
diffractogram produced
during an X-ray scan
Example of an X-ray powder
diffractogram produced
during an X-ray scan
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Why???
Why