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Beta Decay: Energy, Neutrinos & Particle Physics

Learn how beta decay works, including maximum energy of beta particles, reverse decay processes, and key contributions by Enrico Fermi and Wolfgang Pauli. Explore equations and concepts related to mass defect and energy calculations.

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Beta Decay: Energy, Neutrinos & Particle Physics

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  1. b • Beta Decay • Contents: • What it is • (Maximum) Energy of radiation from mass defect Beta- • Whiteboard • (Maximum) Energy of radiation from mass defect Beta+ • Whiteboard • Reverse decay: electron capture • Enrico Fermi, Wolfgang Pauli, and the “little neutral one”

  2. Beta Decay: 6027Co 6028Ni + - +  137N 136C + + +  • 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 TOC

  3. Beta- Decay - Maximum energy of beta particle Calculating mass defect of beta decay 6027Co -->6028Ni + Beta- + (Anti) Neutrino 59.933820 --> 59.930789 + Energy (Look up masses of these in appendix F) (Mass on right includes 28 electrons) Mass defect = parent - products = 59.933820 - 59.930789 Mass “defect” = .003031 u Kinetic energy = (.003031 u)(931.5 MeV/u) = 2.823 MeV This is a maximum - the neutrino carries away some (nucleus as well) TOC

  4. Whiteboards: Beta- Maximum Energy 1 | 2 TOC

  5. 2411Na --> 2412Mg + - + (anti) 23.990961 --> 23.985042 What is maximum energy of Beta-? (in MeV) Parent mass = 23.990961 u Product mass = 23.985042 u Mass defect = parent - products = 0.005919 u Energy of radiation = (0.005919 u)(931.5 MeV/u) = 5.51 MeV W 5.51 MeV

  6. 3114Si --> 3115P + - + (anti) 30.975362 --> 30.973762 What is maximum energy of Beta -? (in MeV) Parent mass = 30.975362 u Product mass = 30.973762 u Mass defect = parent - products = 0.001600 u Energy of radiation = (0.001600 u)(931.5 MeV/u) = 1.49 MeV W 1.49 MeV

  7. Beta+ Decay - Maximum energy of beta+ Calculating mass defect of beta+ decay 137N ---> 136C + Beta+ + Neutrino 13.005738 --> 13.003355 + 2me+ Energy (Carbon 6 mass includes only 6 electrons, we add two - orbital, Beta ) 13.005738 --> 13.003355 + 2(.00054858 u) + Energy 13.005738 --> 13.00445216 + Energy Mass defect = parent - products = 13.005738 - 13.00445216 Mass “defect” = 0.00128584 u Kinetic energy = (0.00128584 u)(931.5 MeV/u) = 1.20 MeV This is a maximum - the neutrino carries away some (nucleus as well) TOC

  8. Whiteboards: Beta+ Maximum Energy 1 | 2 TOC

  9. 158O --> 157N + + +  15.003065 --> 15.000108 + 2(.00054858) What is maximum energy of Beta+? (in MeV) Parent mass = 15.003065 u Product mass = 15.000108 + 2(.00054858) = 15.00120516 Mass defect = parent - products = 0.00185984 energy of radiation = (0.0018598)(931.5 MeV/u) = 1.732 MeV W 1.732 MeV

  10. 4019K --> 4018Ar + + +  39.964000 --> 39.962384 + 2(.00054858) What is maximum energy of Beta+? (in MeV) Parent mass = 39.964000 u Product mass = 39.962384 u + 2(.00054858) = 39.96348116 Mass defect = parent - products = 0.00051884 u Energy of radiation = (0.00051884)(931.5 MeV/u) = 0.4833 MeV W 0.4833 MeV

  11. Reverse Beta - electron capture 74Be + e- --> 73Li +  Nucleus captures inner shell electron Proton becomes neutron Product less massive than parent and electron Energy is released as neutrino X-rays observed as electron jumps down to fill inner shell TOC

  12. 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

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