Beta Decay Contents: What it is (Maximum) Energy of radiation from mass defect Beta- Whiteboard

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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