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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6027Co 6028Ni + - + e
137N 136C + + + e
Energy is continuous (i.e. neutrino gets random share)
Pauli, Fermi, and the little neutral one
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
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
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)
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
1 | 2
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
24596Cm --> 24596Cm +
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