Radioactive Transitions Flashcards
what is radiation in the form of?
Energetic particles or photons
In in-vivo nuclear medicine procedures what is the desirable range to use a radionuclide?
100-500 keV
What is particle radiation?
Byproduct of the transition requiredfor desirable photon emissions
What are the two types of changes that occur within a nucleus?
- loss of energy
2. Change in atomic number in an isobaric transition
Why does the transition always move downward?
The nucleus is decreasing energy by emitting radiation
What are the steps of radioactive transition?
- Isobaric transition
- Isomeric transition
- Interaction with orbiting electrons
What are the 3 types of isobaric transition?
- Beta emission
- Positron emission
- Electron capture
What is crucial in nuclear stability?
neutron-proton ratio
What happens if the neutron-proton ratio (N/P) is too low or too high?
The nucleus will eventually rearrange itself into a more stable configuration
What is Beta radiation and what does it result in?
- Emission of energetic electrons
2. N/P ratio is too high for stability
What occurs when it is too low for stability?
- Positron emission
2. Electron capture
How is the condition relieved if the N/P is too high for stability?
Conversion of an internal neutron into a proton accompanied by the emission, from the nucleus, of an electron
What are the two functions of electron or beta particle?
- Carry away from the nucleus a one-unit negative charge so that a neutron can be converted into a proton with a one-unit positive charge,
- carry off a portion of the energy given up by the nucleus
What is the average beta energy?
usually between 25% and 30% of the maximum energy
What is a positron?
A small particle that has essentially the same mass as an electron but has a positive rather than negative electrical charge
What is the transition energy shared between?
Positron and a neutrino
What happens when a positron particle is formed?
A proton is converted into a neutron
What must the total transition energy be for positron emission to occur?
1.8 MeV
How can a nucleus relieve neutron-proton ratio by?
Absorbing an electron from a shell
What does electron capture create?
Vacancy in one shell
Quickly filled by an electron from a higher energy location
When is Auger electrons produced?
When the energy given up by an electron filling the K-shell vacancy is transferred to another electron, knocking it out of its shell
What do most Auger electrons have?
Relatively low energies
What will nuclei in the intermediate state undergo?
isomeric transition by emitting energy and dropping to the ground state
In most isomeric transition, what will nucleus emit its excess energy in the form of?
Gamma photon
What is a gamma photon?
Small unit of energy that travels with the speed of light and has no mass
What are the photon energies useful for diagnostic procedures?
Range of 100 keV to 500 keV
What is the energy of a gamma photon determined by ?
Difference in energy between the intermediate and final states of nucleus undergoing isomeric transition
What does alpha particle consist of?
Two neutrons and two protons
How are beta emitters created?
neutron bombardment
How can neutrons be obtained?
nuclear reactors or accelerators
