Nuclear Physics

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Nuclear Physics

• PHY 361
• 2008-04-21

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Outline

• history
• structure of the nucleus
• nuclear binding force
• liquid drop model
• shell model magic numbers
• binding energy
• chart of nuclides
• line of stability, drip line, island of stability
  
• radioactivity
• ?,?,? decay
• fission, fusion

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History

• Becquerel discovered radioactivity (1896)
• Rutherford nuclear model
• classified ?,?,? radiation, ? particle 4He
  nucleus
• used ? scattering to discover the nuclear model
• postulated neutrons AZN (1920) bound p e-
  state?
• Mosley studied nucleus via X-ray spectra
• correlated (Z charge of nucleus) with periodic
  table
• extra particles in nucleus A Z ?
• Chadwick discovered neutron (1932)
• Pauli postulated neutral particle from ?-decay
  (1930)
• Fermi theory or weak decay (1933) neutrino
• Fission Hahn, Strassmann, (Meitner!) (1938)
• first reactor (chain reaction), Fermi (1942)
• Bohr, Wheeler liquid drop model
• Mayer, Jensen shell model (1949)
• Hofstadter electron scattering (1953-)
• measured the charge density of various nuclei
• discovered structure in the proton (not
  point-like particle)

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Nuclear potential

• strong force Coulomb repulsion (p-p)
• finite square potential
• hard core const. density

Hofstadter, electron scattering
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Liquid drop model of the nucleus

• constant density like a liquidR R0 A1/3 where
  R0 1.2 fm? A / (4/3 ?R3) 1014 g/cm3 !
• finite square potential
• p,n act as free particles inside of drop
• states filled to Fermi energy
• surface tension
• normally prevents breakup
• excitation can induce split into smaller drops
  with lower overall energy

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Shell model of the nucleus

• 1949 M. Mayer, J.H.D. Jensen
• similar to atomic orbitals
• quantized angular momentum
• energy levels
• multi-particle wave function

• difference
• no central potential (nucleus)
• effective finite square potential
• complicated nuclear force
• strong dependence on spin
• two particles p, n
• more types of decays

nucleus
atom
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Chart of Nuclides binding energy

• AZXNq ex. 1H, 2H, 3He, 4He
• A Z N protons neutrons
• B Z MHc2 N mnc2 - MAc2
• nuclides Z,N
• isotope constant Z (same place)
• isotone constant N (isotone)
• isobar constant A (same weight)
• isomer excited state or nuclide

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Chart of Nuclides lifetime
magic numbers
http//www.nndc.bnl.gov/chart
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Chart of Nuclides decay mode
magic numbers
stable nuclide ?- decay ??, electron
capture ??decay p decay n decay spontaneous
fission
http//www.nndc.bnl.gov/chart
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Chart of Nuclides island of stability
magic numbers
http//en.wikipedia.org/wiki/Island_of_stability
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Nuclear decay modes

• ? decay
• ?- decay (isobar)
• ? decay (isobar)
• ? electron capture (isobar)
• p decay (isotone)
• n decay (isotope)
• ? decay (isomers)
• electron conversion (EC)
• spontaneous fission (SF)
• double beta decay (2???)
• neutrino-less double beta decay (0???)
• beta-delayed n,p,? decay

ISOBARS
ISOTONES
ISOMERS
ISOTOPES
Z
N
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Alpha-decay
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Beta-decay