Semi-empirical mass formula and fission term

In summary, the term responsible for fission in the semi-empirical mass formula is the symmetry term, which is due to the Pauli exclusion principle preventing same states from being occupied. The positive Q-value for fission in nuclides heavier than 92Mo is not enough to overcome the barrier set by the symmetry term, explaining why spontaneous fission cannot occur.
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Ryomega
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Homework Statement



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.

Homework Equations



Semi-empirical mass formula:

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

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?

Help.:cry:
 
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^bump
 
  • #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.
 

Related to Semi-empirical mass formula and fission term

1. What is the Semi-empirical mass formula?

The Semi-empirical mass formula is an equation that is used to calculate the approximate nuclear binding energy of an atomic nucleus. It takes into account the number of protons and neutrons in the nucleus, as well as various correction terms such as the pairing term and the asymmetry term.

2. How is the Semi-empirical mass formula derived?

The Semi-empirical mass formula is derived from experimental data on nuclear masses and binding energies. By using regression techniques, scientists have found a formula that closely approximates the data and can be used to calculate nuclear binding energies for any given nucleus.

3. What is the fission term in the Semi-empirical mass formula?

The fission term in the Semi-empirical mass formula takes into account the energy released during nuclear fission, which is the process of splitting an atomic nucleus into smaller fragments. This term helps to account for the decrease in binding energy as a nucleus becomes more unstable and undergoes fission.

4. How does the fission term affect the stability of a nucleus?

The fission term can greatly affect the stability of a nucleus. As the number of protons and neutrons in a nucleus increases, the fission term becomes more significant and can lead to a decrease in stability. This is why larger nuclei tend to be more unstable and are more likely to undergo fission.

5. Can the Semi-empirical mass formula accurately predict nuclear binding energies?

The Semi-empirical mass formula is a very useful tool for predicting nuclear binding energies, but it is not perfect. It is based on approximations and does not take into account all factors that may affect nuclear stability. However, it is still widely used in nuclear physics research and has been shown to provide reasonably accurate results.

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