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Questions and Answers
What is the typical state of a nucleus after it disintegrates by emitting alpha, beta or any other kind of particle?
What is the typical state of a nucleus after it disintegrates by emitting alpha, beta or any other kind of particle?
What is the minimum energy required for the creation of internal pairs?
What is the minimum energy required for the creation of internal pairs?
What is the characteristic of the Gamma-ray spectra of excited nuclei?
What is the characteristic of the Gamma-ray spectra of excited nuclei?
What is the process by which a nucleus in an excited state transitions to a lower energy state?
What is the process by which a nucleus in an excited state transitions to a lower energy state?
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In which type of nuclei is internal conversion more frequent?
In which type of nuclei is internal conversion more frequent?
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What is the alternative to gamma-ray emission in nuclear reactions?
What is the alternative to gamma-ray emission in nuclear reactions?
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What is the term for radioactive nuclei produced in the laboratory?
What is the term for radioactive nuclei produced in the laboratory?
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What is the term for the initial radioactive isotope in a decay chain?
What is the term for the initial radioactive isotope in a decay chain?
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Why do elements with atomic numbers between Z=81 and Z=92 have many radioisotopes?
Why do elements with atomic numbers between Z=81 and Z=92 have many radioisotopes?
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What happens to the nucleus when it decays by emitting α-rays?
What happens to the nucleus when it decays by emitting α-rays?
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What happens to the charge on the nucleus during beta decay?
What happens to the charge on the nucleus during beta decay?
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What is the change in mass number of a nucleus that decays by emitting α-rays?
What is the change in mass number of a nucleus that decays by emitting α-rays?
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What happens to the probability inside the barrier?
What happens to the probability inside the barrier?
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What type of decay involves the emission of a positron?
What type of decay involves the emission of a positron?
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What is a necessary condition for spontaneous decay?
What is a necessary condition for spontaneous decay?
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What is the process in which a neutron is converted into a proton and an electron is emitted?
What is the process in which a neutron is converted into a proton and an electron is emitted?
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Why do low-E alpha particle emitters have long half-lives?
Why do low-E alpha particle emitters have long half-lives?
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What is the energy available for the disintegration by beta emission?
What is the energy available for the disintegration by beta emission?
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Study Notes
Alpha Decay
- Inside the barrier, the probability of alpha decay decreases exponentially, explaining why low-energy alpha-particle emitters have long half-lives.
Beta Decay
- Beta decay includes β- decay, β+ decay, and EC (Electron Capture) decay.
- Electrons or positrons cannot exist inside the nucleus, so they are created at the moment of nucleus disintegration.
- During EC, the electron is captured by the nucleus, disappearing and converting its mass into energy.
Conditions for Spontaneous Decay
- Using the principle of conservation of energy, we can determine whether an unstable beta nucleus will decay through β- emission, β+ emission, or electron capture.
- The three processes can be represented as:
- β- emission: a proton becomes a neutron, and an electron is emitted.
- β+ emission: a neutron becomes a proton, and a positron is emitted.
- Electron Capture (EC): a proton in the nucleus captures an electron, becoming a neutron.
Energy Available for Disintegration
- Conserving energy, we can show that the energy available for beta emission is related to the masses of the parent (X) and daughter (Y) nuclei and the electron (e).
Gamma Decay
- When a nucleus disintegrates, it is usually left in an excited state, which can lead to gamma-ray emission, internal conversion, or the creation of internal pairs.
- These processes are caused by electromagnetic interactions.
- Internal conversion is more frequent in heavy excited nuclei, while the creation of internal pairs is more frequent in light nuclei and requires energy > 1.02 MeV.
Gamma-Ray Emission
- Gamma-ray spectra of excited nuclei consist of discrete energies, indicating discrete energy levels in the nucleus.
- Nuclei can decay through alpha or beta emission, leaving them in discrete excited energy states.
Radioactive Decay
- There are approximately 65 radioactive nuclei found in nature.
- Radioactive nuclei produced in the laboratory exhibit artificial radioactivity, with over 1000 isotopes produced.
- Both naturally occurring and artificially produced radioactive isotopes often decay through successive disintegration.
- The parent-daughter-granddaughter decay chain continues until the nucleus reaches stability.
Radioactive Isotopes
- Radioisotopes are common among elements with atomic numbers between Z=81 and Z=92 due to Coulomb repulsion between protons.
- To decrease the Coulomb repulsive force, unstable nuclei decay by emitting α-rays, losing two protons and two neutrons.
- This leads to an excess of neutrons, causing the nucleus to decay further by emitting β-rays, converting a neutron to a proton.
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Description
Test your understanding of nuclear reactions, including beta decay, gamma decay, and the resulting excited states of nuclei. Learn about the postulates of Lee and Yang and the behavior of particles in these reactions.
