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Homework Help: Semi-empirical mass formula and fission term

  1. Jan 28, 2012 #1
    1. The problem statement, all variables and given/known data

    Which term in semi-empirical mass formula gives rise to the energy release in fission? What is the physical origin of this term? All β-stable nuclides heavier than 92Mo (Molybdenum) have a positive Q-value for fission; explain what prevents them decaying in this way.

    2. Relevant equations

    Semi-empirical mass formula:

    Energy (Binding) = Volume term - Surface term - Coulomb repulsion term - a/symmetry term - pairing term

    3. The attempt at a solution

    I know that Z2/A ≥ 49 gives spontaneous fission. So that makes the symmetry term responsible for fission. The origin is Pauli exclusion principle where no same states can be occupied.

    The rest of the question is complete gibberish to me. I'm not even sure WHCIH way is decaying for what WHAT way is decaying what?

  2. jcsd
  3. Jan 29, 2012 #2
  4. Feb 18, 2012 #3
    The Q value is the energy released during the reaction. A positive Q-value implies that the reaction may be possible.
    However, if you look up the values of Z and A for 92Mo and put them into your formula: [tex]\frac{Z^2}{A}\geq49[/tex] you will find out why spontaneous fission cannot occur.
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