Nuclear Physics PHY

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

History  Becquerel – discovered radioactivity (1896)  Rutherford – nuclear model classified , ,  radiation,  particle = 4 He 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 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)

Nuclear potential  strong force + Coulomb repulsion (p-p)  ~ finite square potential  hard core – const. density Hofstadter, electron scattering

Liquid drop model of the nucleus  constant density like a liquid R = R 0 A 1/3 where R 0 ~ 1.2 fm  = A / (4/3  R 3 ) = g/cm 3 !  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

nucleusatom 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

Chart of Nuclides – binding energy  A Z X N q ex. 1 H, 2 H, 3 He, 4 He  A = Z + N = # protons + # neutrons  B = Z M H c 2 + N m n c 2 - M A c 2  nuclides – Z,N isotope – constant Z (‘same place’) isotone – constant N (isoto‘n’e) isobar – constant A (‘same weight’) isomer– excited state or nuclide

Chart of Nuclides – lifetime magic numbers

Chart of Nuclides – decay mode stable nuclide  - decay  , electron capture  decay p decay n decay spontaneous fission magic numbers

Chart of Nuclides – island of stability magic numbers

N Z 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 ISOTOPES ISOTONES ISOMERS

Alpha-decay

Beta-decay