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Beta and Gamma Decay Contents: Beta What it is and the Neutrino Hypothesis

Beta and Gamma Decay Contents: Beta What it is and the Neutrino Hypothesis Reverse decay: electron capture Enrico Fermi, Wolfgang Pauli, and the “little neutral one” Gamma What it is Being Discrete Whiteboards. b. g. Beta Decay:. 60 27 Co 60 28 Ni + - +  e.

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Beta and Gamma Decay Contents: Beta What it is and the Neutrino Hypothesis

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  1. Beta and Gamma Decay • Contents: • Beta • What it is and the Neutrino Hypothesis • Reverse decay: electron capture • Enrico Fermi, Wolfgang Pauli, and the “little neutral one” • Gamma • What it is • Being Discrete • Whiteboards b g

  2. Beta Decay: 6027Co 6028Ni + - + e 137N 136C + + + e • Conservation of charge • Beta minus - electron • “As if” neutron -> proton + electron • Beta plus - positron • “As if” proton -> neutron + positron • Particles are “of the nucleus” (not orbital) • - Neutrino, (anti neutrino) – fudge (Conserve lepton number) Energy is continuous (i.e. neutrino gets random share) TOC

  3. Pauli, Fermi, and the little neutral one Wolfgang Pauli 1900-1958 Enrico Fermi 1901-1954 Beta decay products were missing energy Pauli proposes a particle is carrying away energy Fermi names it Neutrino - “Little neutral one” - It. Neutrinos confirmed in 1956, no surprise TOC

  4. ne e

  5. Gamma Decay: 23994Pu 23994Pu +  Nucleus has energy levels Energy of transition emitted as a high energy photon ( ≈ 5 - .05 nm) Usually after a beta or alpha decay Many energies possible Stopped by meters of lead Used for food irradiation TOC

  6. Example: Tl-208 emits a 0.6210 MeV gamma and the neutral (un -excited) atom has a mass of 207.9820047 u. What was the mass before the gamma was emitted? Gamma ray energies associated with alpha and beta decays – so Alpha and Gamma energies are discrete. (Like spectral lines we saw)

  7. Example: Tl-208 emits a 0.6210 MeV gamma and the neutral atom has a mass of 207.9820047 u. What was the mass before the gamma was emitted? Well, 0.6210 MeV has a mass of (0.6210 MeV)/(931.5 MeV) = 0.000666667 u So the parent is this much more massive: 207.9820047 + 0.000666667 = 207.9826714 u

  8. Whiteboards: Gamma Decay 1 | 2 TOC

  9. 23994Pu --> 23994Pu +  239.052464 --> 239.052157 What is the energy of the gamma emitted? Parent mass = 239.052464 u Product mass = 239.052157 u Mass defect = parent - products = 0.000307 u Energy of radiation = (0.000307 u)(931.5 MeV/u) = 0.2860 MeV W 0.2860 MeV

  10. 24596Cm --> 24596Cm +  ???.?????? --> 245.065486 What is the excited mass of the parent, if a 0.2957 MeV gamma photon is emitted? Mass of 0.2957 MeV = (0.2957 MeV)/(931.5 MeV/u) = 0.000317445 u Excited parent is more massive than this by that amount Parent mass = 245.065484 + 0.000317445 u = 245.0658034 u W 245.0658034 u

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