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


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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

  • 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 and gamma decay contents beta what it is and the neutrino hypothesis

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


Beta and gamma decay contents beta what it is and the neutrino hypothesis

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


Beta and gamma decay contents beta what it is and the neutrino hypothesis

ne

e


Beta and gamma decay contents beta what it is and the neutrino hypothesis

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


Beta and gamma decay contents beta what it is and the neutrino hypothesis

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)


Beta and gamma decay contents beta what it is and the neutrino hypothesis

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


Beta and gamma decay contents beta what it is and the neutrino hypothesis

Whiteboards:

Gamma Decay

1 | 2

TOC


Beta and gamma decay contents beta what it is and the neutrino hypothesis

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


Beta and gamma decay contents beta what it is and the neutrino hypothesis

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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