1. INTRODUCTION
X –RAYS: The X-ray region of electromagnetic spectrum
consists of shortest wavelength in the region of about 0.1 to
100AO
For analytical purposes ,the range of 0.7 to 2.0AOis mostly
used.
2
3. DISCOVERY
X-rays were discovered by W.C.Rontgen is a german
physicist in 1895.
For his work Rontgen awarded the first ever Nobel prize
for physics in 1901
4
4. ORIGIN OF X-RAYS
X-rays are generated when high velocity electrons impinge
on a metal target .
The process of producing X-rays may be visualized in
terms of Bohr’s theory of atomic structure.
5
5. Whenever a fast moving electron impinges on an atom, it
may knock out an electron completely from one of the
inner shells of that atom.
Following the loss of inner-shell electron one of the outer
electrons will fall in to the vacated orbital ,by the emission
of x-rays.
6
6. The energy of the emitted X-ray photon is equal to the
difference in energy between two levels involved.
E = E2-E1
E2 and E1 are the final and initial energies which are
emitted from L and K shells respectively
If the vacancy produced in the K-shell is filled by the
electron from L-shell, the radiation is called Kὰ .
Electron from M-shell it is called Kβ.
7
7. The frequency of emitted radiation is given by
ϑ= Z² (2∏2me/h3)(1/N1
2 –1/N2
2 )
Z = Atomic number of an atom
m = mass of the electron
e = charge of the electron
h = plank's constant
N1 , N2 =1 & 2 for K&L shell
8
11. In 1912 von Laue placed a crystal of copper sulphate
between a white x-ray source and photographic plate
The resulting photograph observed here:
12
17. GENERATION OF X-RAYS
X-rays are generated when high velocity of electrons
impinge on a metal target.
Approximately 1% of total energy of electron beam is
converted in to x –radiation.
Two type of devices are used for generating x-rays
1) X-ray tube
2) Synchrotron radiation
18
19. Synchrotron radiation
Synchrotron radiation is emitted by electron and positrons
travelling at near light speed in circular storage ring.
Powerful sources which are thousands to millions of times
more intense than x-ray tubes.
20
20. COLLIMATOR
The x-rays produced by the target material are randomly
directed.
In order to get a narrow beam of x-rays ,they are allowed to
pass through a collimator which consist of two sets of
closely packed metal plates separated by a small gap.
The collimator absorbs all the x-rays except the narrow that
passes between the gap.
21
21. MONOCHROMATORS
Mainly two types:
a)FILTERS: It is a window of material that absorbs
undesirable radiation but allows the radiation of wave to
pass.
e.g. :Zirconium filter
which is used for molybdenum radiation.
22
22. some more examples of beta filters:
b)Crystal monochromators
1)Flat crystal monochromator
2)Curved crystal monochromator
TARGET
ELEMENT
ß-FILTERS THICKNESS %LOSS IN K∞
INTENSITY
Co Fe 0.012 39
Cu Ni 0.015 45
Fe Mn 0.011 38
Mo Zr 0.081 57
Ni Co 0.013 42
23
23. CRYSTAL MONOCHROMATOR: The beam is split into
component wavelength by the crystal line material such
material is called as Analyzing crystal.
Crystals used in monochromators are sodium chloride,
lithium fluoride, quartz etc.
24
24. DETECTORS
1) photographic method
2)counter methods
a) Geiger - Muller tube method
b) proportional counter
c) scintillation detector
d) solid-state semiconductor detector
e)semi conductor
25
25. PHOTOGRAPHIC METHOD
PRINCIPLE :
By using plane or cylindrical film
Developing the film
D=log Io/I
D is the total energy
Measured by using densitometer
USES: For diffraction studies
For quantitative measurement
DIS ADVENTAGES: Time consuming
26
26. SCINTILLATION DETECTOR
Its mainly contains a large crystal of
sodium iodide activated with small
amounts of thallium.
They convert incident x-rays in to visible
light which is detected by photo
multiplier tube.
e.g. for crystals :
sodium iodide , anthracene,
naphthalene ,p- terpenol in xylene.
Used for short wavelengths
27
27. PROPORTIONAL COUNTER METHOD:
It is filled with heavier gas like xenon ( or) krypton
it is preferred because it is easily ionized.
More efficiency and sensitive
28
28. GIEGER MULLER COUNTER
PRINCIPLE: Ionization of argon gas which is filled in the
Geiger tube by x-rays.
ADVANTAGES: In expensive
Trouble-free
DISADVANTAGES: only for counting low rates
Efficiency will be less
29
29. SOLID- STATE SEMI CONDUCTOR
DETECTOR:
Electrons produced by x-ray beams are converted
in to conduction bands ,the current which flows
is directly propotional to incident x-rays.
SEMI CONDUCTOR DETECTOR:
A pure silicon block set up with a thin film
lithium metal placed on to one end.
Semi conductor
30
30. X-RAY DIFFRACTION METHODS
1) SINGLE CRYSTAL DIFFRACTOMETER:
A) LAUE METHOD
a)TRANSMISSON METHOD
b)BACK REFLECTION METHOD
B) BRAGG’S SPECTROPHOTOMETER METHOD
2)POWDER CRYSTAL DIFFRACTOMETER
31
39. 3)PARTICLE SIZE DETERMINATION:
a)Spot counting method:
b)Broadening of diffraction lines
c)Low-angle scattering
4)APPLICATIONS OF DIFFRACTION METHODS TO
COMPLEXES:
a)Determination of cis-trans isomer
b)Determination of linkage isomer
40
40. 5)STATE OF ANNEAL IN METALS :
Well annealed metals are in well ordered crystal form and give
sharp diffraction lines.
If the metal breaking is present then the x-ray pattern more
diffuse.
6)MISCELLANEOUS APPLICATIONS:
Soil classification based on crystallinity
Analysis of industrial dusts
Weathering and degradation of naturals and synthetic
minerals
Corrosion products can be studied by this method
Tooth enamel and dentine have been examined by X-ray
diffraction.
41