Nuclear Physics
PHY 361
2008-04-21
Outline
 history
 structure of the nucleus
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nuclear binding force
liquid drop model
shell model – magic numbers
 binding energy
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chart of nuclides
line of stability, drip line, island of stability
 radioactivity
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,, decay
fission, fusion
History
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Becquerel – discovered radioactivity (1896)
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Rutherford – nuclear model
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classified ,, radiation,  particle = 4He nucleus
used  scattering to discover the nuclear model
postulated ‘neutrons’ A=Z+N (1920); bound p+ e- state?
Mosley – studied nucleus via X-ray spectra
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correlated (Z = charge of nucleus) with periodic table
extra particles in nucleus: A = Z + ?
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Chadwick – discovered neutron (1932)
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Pauli – postulated neutral particle from -decay (1930)
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Fermi – theory or weak decay (1933) ‘neutrino’
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Fission – Hahn, Strassmann, (&Meitner!) (1938)
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first reactor (chain reaction), Fermi (1942)
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Bohr, Wheeler – liquid drop model
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Mayer, Jensen – shell model (1949)
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Hofstadter – electron scattering (1953-)
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measured the charge density of various nuclei
discovered structure in the proton (not point-like particle)
Nuclear potential
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strong force + Coulomb repulsion (p-p)
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~ finite square potential
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hard core – const. density
Hofstadter, electron scattering
Liquid drop model of the nucleus
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constant density like a liquid
R = R0 A1/3 where R0 ~ 1.2 fm
 = A / (4/3 R3) = 1014 g/cm3 !
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finite square potential
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p,n act as free particles inside of drop
states filled to Fermi energy
‘surface tension’
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normally prevents breakup
excitation can induce split into smaller
drops with lower overall energy
Shell model of the nucleus
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1949 – M. Mayer, J.H.D. Jensen
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similar to atomic orbitals
difference:
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quantized angular momentum
energy levels
multi-particle wave function
nucleus
no ‘central’ potential (nucleus)
effective finite square potential
complicated nuclear force
strong dependence on spin
two particles: p, n
more types of decays
atom
Chart of Nuclides – binding energy
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A X q
Z N
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A = Z + N = # protons + # neutrons
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B = Z MHc2 + N mnc2 - MAc2
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nuclides – Z,N
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ex. 1H, 2H, 3He, 4He
isotope
isotone
isobar
isomer
– constant Z (‘same place’)
– constant N (isoto‘n’e)
– constant A (‘same weight’)
– excited state or nuclide
Chart of Nuclides – lifetime
magic numbers
http://www.nndc.bnl.gov/chart
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
Chart of Nuclides – island of stability
magic numbers
http://en.wikipedia.org/wiki/Island_of_stability
Nuclear decay modes:
++ decay
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- decay (isobar)
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+ decay (isobar)
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 electron capture (isobar)
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p decay (isotone)
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n decay (isotope)
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 decay (isomers)
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electron conversion (EC)
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spontaneous fission (SF)
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double beta decay (2)
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neutrino-less double beta decay (0)
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beta-delayed n,p, decay
ISOTONES
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ISOMERS
ISOTOPES
Z
N
Alpha-decay
Beta-decay