1. b g 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)
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3. Pauli, Fermi, and the little neutral one
Wolfgang Pauli
Enrico Fermi
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
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5. ne e

6. Gamma Decay: 23994Pu 23994Pu +  Nucleus has energy levels
Energy of transition emitted as a high energy photon ( ≈ nm)
Usually after a beta or alpha decay
Many energies possible
Stopped by meters of lead
Used for food irradiation
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7. Example: Tl-208 emits a MeV gamma and the neutral (un -excited) atom has a mass of 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)

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

9. Whiteboards:
Gamma Decay
1 | 2
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10. 23994Pu > Pu + 
>
What is the energy of the gamma emitted?
Parent mass = u
Product mass = u
Mass defect = parent - products = u
Energy of radiation = ( u)(931.5 MeV/u)
= MeV W
MeV

11. 24596Cm --> Cm + 
???.?????? -->
What is the excited mass of the parent, if a MeV gamma photon is emitted?
Mass of MeV = ( MeV)/(931.5 MeV/u)
= u
Excited parent is more massive than this by that amount
Parent mass = u = u W u