1. X-RAY CRYSTALLOGRAPHY
DIFFERENT X RAY METHODS AND PRODUCTION OF X RAYS
M.PHARM 1ST SEM PHARMACEUTICS
DEPARTMENT OF PHARMACEUTICAL SCIENCES
DR. SUDIPTA SAHA
DEPARTMENT OF PHARMACEUTICAL SCIENCES
WHAT IS X RAY
WHAT IS CRYSTAL
WHY X RAY IS USED
WHY CRYSTALS ARE USED
DIFFERENT X RAY METHODS
PRODUCTION OF X RAY
X-ray crystallography is a technique used for determining the atomic
and molecular structure of a crystal
The crystalline atoms cause a beam of incident X-rays to diffract into
many specific directions.
By measuring the angles and intensities of these diffracted beams, a
crystallographer can produce a three-dimensional picture of the
density of electrons within the crystal.
From this electron density, the mean positions of the atoms in the
crystal can be determined, as well as their chemical bonds, their
disorder, and various other information.
5. PRINCIPLE OF X RAY CRYSTALLOGRAPGY
Principle of X ray crystallography is that the crystalline atoms
cause beam of X rays to diffract into many specific directions.
A crystal can be described with the aid of grid or lattice, defined by
three axis and angles between them.
X ray crystallography uses the principle of X ray diffraction to analyze
the sample, but is done in many different directions so that the 3D
structure can be buildup.
It is a technique that has helped to deduce the 3D crystal
structure of many materials, especially biological materials.
7. WHAT IS X RAY ?
X rays are the beam of electromagnetic radiation.
These are of smaller wavelength than visible light.
Wavelength of X ray - 0.01-10 nm
Analytical purpose - 0.07-0.2 nm
X rays have higher energy.
They are more penetrative.
9. WHAT IS CRYSTAL ?
A crystal is a solid whose
atoms are arranged in a
highly ordered repeating
These patterns are called as
10. WHY X RAYS ARE USED ?
X rays have wavelength similar to the size of an atom.
X rays have smaller wavelength than visible light so they have
higher energy and can penetrate the matter more easily than
the visible light.
11. WHY CRYSTALS ARE USED ?
When sample is present in liquid form , the bond angle keep
changing , the position of atoms keep changing in every
moment so it is very hard to determine the structure of that
So when we change biological liquid sample in crystalline form
(solid form) , the conformation of molecule is fixed in a single
place , so it makes easy to determine the structure of that
12. DIFFERENT X RAY METHODS
1) X ray absorption method
2) Auger X ray emission method
3) X ray fluorescence method
4) X ray diffraction method (XRD)
13. 1. X RAY ABSORPTION METHOD
This method is similar to absorption in other regions of
electromagnetic spectra like UV-Visible / IR spectroscopy etc.
Wavelength at which a sudden change in absorption occurs is used
to identify an element present in a sample, and the magnitude of
the change determines the amount of particular element present.
14. 2. AUGER X RAY EMISSION
The primary X-rays eject electrons from
inner energy level
Just outer level electrons fall into vacant
inner levels by non radiative processes.
Excess energy ejects electrons from outer
15. 3. X RAY FLUOROSCENCE METHOD
The primary X-ray ejects electron from
inner energy levels where the wavelength
is equal to absorption edge.
But when the wavelength is shorter than
absorption edge it emits secondary X-ray
when electrons fall into inner vacant
16. 4. X RAY DIFFRACTION MRTHOD(XRD)
X ray diffraction works by irradiating a material with incident x
ray and then measuring the intensities and scattering angles of
the x ray that leave the material.
When a beam of monochromatic X ray is directed at a crystalline
material, one observes reflection or diffraction of the X-rays at a
various angle with respect to the primary beam
The relationship between the X-ray , angle of diffraction and
distance between each set of atomic planes of crystal lattice is given
by Braggs equation-
20. 1) PRODUCTION OF X RAYS
X rays are produced inside the X ray tube when high energy
projectile electrons from the filament interact with the atoms of
X ray tube (Coolidge tube) : It is a large vacuum tube
containing a heated cathode of tungsten filament and copper or
molybdenum target metal anode.
• Operated at higher voltage up to 60 KV.
There is cathode which is a filament of tungsten metal heated by a
battery to emit the thermionic electrons.
This beam of electrons moves towards anode target and attain
the kinetic energy and 99% of energy is converted into heat via
collision and remaining 0.5-1% is converted to X rays.
Generally the target gets very hot in use so this problem has been
solved to some extent by cooling the tube with water.
26. WHAT HAPPENS ACTUALLY ?
If sufficiently energetic electrons are available, the transfer of energy
from the impinging electron beam may eject an electron from one of
the inner levels of the target atoms.
Within each atom, the place of the ejected electron is promptly filled
by an electron from an outer level whose place, in turn is taken by an
electron coming from still farther out.
Thus the ionized atom returns to its normal state in as series of steps,
in each of which an X-ray photon of definite energy is emitted or
excess energy is released by ejection of a second electron with
The k series of line is observed when
an electron in the innermost K level
(n=1) is dislodged and electrons drop
down from the L (n=2) or M (n=3)
levels into the vacancy in k level.
Corresponding vacancies in the L
levels are filled by electron
transitions from outer levels and give
rise to L series.
Disadvantage of most of X-ray tubes is that there is lack of focusing
of electrons so that whole surface becomes a source of X-rays.
29. 2) COLLIMATOR
It used to get the narrow beam of X rays.
To get a narrow beam of X-rays, the X-rays
generated by the target material are allowed to
pass through a collimator which consists of two
sets of closely packed metal plates separated by a
The collimator absorbs all the X-rays except the
narrow beam that passes between the gaps.
I. FILTER MONOCHROMATOR-
A filter is a window of material that absorbs undesirable radiation but
allows the radiation of required wavelength to pass.
II. CRYSTAL MONOCHROMATOR-
A crystal monochromator is made up of a suitable crystalline material
positioned in the X-ray beam so that the angle of reflecting planes
satisfied Bragg’s equation for the required wavelength.
33. 4) DETECTOR
I. PHOTOGRAPHIC METHOD-
In order to record the position and intensity of X-ray beam a plane or
cylindrical film is used.
The film after exposing to X-rays is developed. The blackening of the
developed film is expressed in terms of density units D given by
D = log I˳/I
II. COUNTER METHODS-
The Geiger tube is filled with an inert gas like argon and the central
wire anode is maintained at a positive potential of 800 to 2500V.
When an X-ray is entering the Geiger tube, this ray undergoes
collision with the filling gas, resulting in the production of an ion
pair: the electron produced moves towards the central anode while
the positive ions move towards outer electrode.
The electron is accelerated by the potential gradient and causes
the ionisation of large number of argon atoms, resulting
production of an avalanche of electrons that are travelling
towards the central anode.
The Geiger tube is in expensive and is relatively trouble free
detector. This tube gives the highest signal for given X-ray
36. APPLICATION OF CRYSTALLOGRAPHY
Characterization of crystalline materials.
Identification of fine-grained minerals such as clays and mixed layer
clays that are difficult to determine optically.
Determination of unit cell dimensions measurement of sample purity.
Determination of Cis- trans isomerism.
Differentiation of sugar.