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Nuclear Physics
History and Overview
• Democritus (4th B.C) - All matter consists of very small, indivisible particles called
atomos.
• John Dalton (1808) - Elements are composed of extremely small particles called
atoms. All atoms of a given element are identical, having the same size, mass, and
chemical properties. The atoms of one element are different from the atoms of all
other elements.
• J. J. Thomson (1900) - An atom could be thought of as a uniform, positive sphere
of matter in which electrons are embedded like raisins in a cake, called ”plumpudding” model.
• Ernest Rutherford (1910) - A positive nucleus orbited by electrons.
• James Chadwick (1932) - Nucleus contains proton and neutron orbited by electrons
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Subatomic particles
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Atomic Structure
Atoms are composed of protons, neutrons and electrons
• Atomic number (Z) is the number of protons in the nucleus of each atom of
an element.
• Mass number (A) is the total number of neutrons and protons present in the
nucleus of an atom of an element.
• Isotope - element with same proton number (A) but different neutron numbers
(N) - Hydrogen, Deuterium & Tritium
• Isotone - element with same neutron number (N) but different proton numbers
(Z) - Deuterium and Helium
• Isobar - element with the same mass number (A) - normal helium and radioactive
Tritium .
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Nuclear Properties
• Mass
• Radius
• Relative abundance (stable nuclides)
• Decay modes and half-life
• Reaction modes and cross section
• Spin
• Magnetic dipole and electric quadrupole moments
• Excited states
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Segre (Nuclides) Chart
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Units
• Energy - electron-volt
1 electron-volt = kinetic energy of an electron when moving through potential
difference of 1 Volt;
– 1 eV = 1.6 x 10-19 Joules
– 1 kW.hr = 3.6 x 106 Joules = 2.25 x 1025 eV
– 1 MeV = 106 eV, 1 GeV= 109 eV, 1 TeV = 1012 eV
• Mass - eV/c2
– 1 eV/c2 = 1.78 x 10-36 kg
– electron mass = 0.511 MeV/c2
– proton mass = 938 MeV/c2 = 0.938 GeV/ c2
– neutron mass = 939.6 MeV/c2
• Momentum - eV/c:
– 1 eV/c = 5.3 x 10-28 kg m/s
– Momentum of baseball at 80 mi/hr ≈ 5.29 kgm/s ≈ 9.9 x 1027 eV/c
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Units
• Distance
– 1 femtometer (”Fermi”) = 10-15 m
• Atomic mass unit is defined in terms of the mass of 126C, with A = 12, Z = 6:
– 1 amu = (mass of 126C atom)/12
– 1 amu = 1.66 x 10-27kg
– 1 amu = 931.494 MeV/c2
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