Nuclear physics

1. Basics of nuclear
physics

2. Contents:
 Structure of an atom
 Rutherford’s atomic model
 Bohr’s atomic model
 Electrons and energy levels
 Nuclear elements and nuclear stability
 Radioactivity
 Decay process
 Interaction of radiation with matter

3. Structure of an atom
 JJ Thomson’s plum pudding model

4. Rutherford’s planetary model
 Rutherford’s experiment: scattering of
alpha particles.

6. Drawbacks:
 According to Larmor theory electron
loses energy while orbiting nucleus.
Hence atom will collapse in 16
picoseconds

7. Bohr’s atomic model
 According to Neil Bohr’s theory electron can have
only classical motions:
◦ Electrons in atoms orbit the nucleus.
◦ The electrons can only orbit stably, without
radiating, in certain orbits at a certain discrete set
of distances from the nucleus.
◦ Electrons can only gain and lose energy by
jumping from one allowed orbit to another,
absorbing or emitting electromagnetic radiation
with a frequency ν determined by the energy
difference of the levels according to the Planck
relation:

8. Electrons and energy levels
 Mass of an electron: 9.1*10-28 g.
 Charge: 1.59*10-19 coulombs.
 A particle with same mass but a
positive charge is called positron.
 No. of electrons in a shell is given by:
2n2 .
 Binding energy of a single electron of
Hydrogen atom: E
b=-13.6/n2 eV

9. Nuclear elements
 Fundamental constituents: neutrons
and protons.
 Mass of proton: 1.672*10-24 g.
 Neutron:
◦ No charge, mass ~ proton.
◦ Limited life in free state. Later
disintegrates into electron and proton.
 Symbol:

10. Nuclear stability
 Stability depends on n/p ratio.
 Extra energy is released by the
nucleus by expelling particles or
photons.

11. Radioactivity
 The process of transmutation of an
unstable element to another element
through the emission of radiation.
 Unit: curie (Ci) (3.7*1010
disintegration/sec).
 Radioactive decay law:
 Half life of an element:

12. Decay Process
It consists of four processes:
Alpha decay
Beta decay
Positron decay
Gamma decay

13. Alpha decay

14. Alpha Decay Applications
?4
2
241
95
A
ZHeAm 

15. Beta decay
AceRa 228
89
0
1
228
88 

16. Positron Emission
ThePa 230
90
0
1
230
91 

17. Gamma Decay
0
0
240
94
240
94  PuPu

18. Decay Process
 Isotopes: Z same, A different
e.g 1H1,1H2, 1H3
 Isobars: A same, Z different
e.g. 40S, 40Cl
 Isotones: Same number of neutrons.
e.g. Cl-37, K-39
 Isomeres: They are different excited
states of the same type of nucleus.
 Electron capture:

19. Isomeric and Isobaric
Transition
 A nuclear process in which a nucleus
following the emission of an alpha
particle or a beta particle emits energy
without changing its number of protons
or neutrons.

20. Interaction of x-rays with
matter
 Phoelectric effect:
 Kinetic energy:EC= EO +EB

21. Compton Effect
 The Compton effect (Compton scattering)
is the result of a high-energy photon
colliding with a target, which releases
loosely bound electrons from the outer
shell of the atom or molecule. The
scattered radiation experiences a
wavelength shift.


22. Pair Production
 Pair production is the creation of
an elementary particle and
its antiparticle, for example
an electron and the positron.
 occurs when a photon interacts with a
nucleus.

23. THANK YOU!!