Presentation Transcript
Chapter 2 Objectives :Chapter 2 Objectives Ben Weisman
Friday, September 8, 2006
Intro to Nuclear Medicine
Group Three
The Processes of Ionization and Excitation :The Processes of Ionization and Excitation These two processes involve the probability that electrically charged particles (alpha particles, electrons, and positrons) will inevitably interact with surrounding particles.
These interactions are ultimately based on the atomic number, the mass number, and the density of the surrounding matter.
In addition, this probability of interaction will provide some information on how far these particles will travel.
Excitation :Excitation Occurs when there is a small amount of energy temporarily absorbed in the outer electron shells of an atom
Energy that passes through the electron shell (in the form of a charged particle or from interactions of electromagnetic radiation) causes these outer electrons to be “excited” or moved to a slightly higher energy level. Since the electron(s) are not removed from the atom, this is not ionization.
Ionization :Ionization Occurs when there is sufficient energy of the passing radiation which allows an electron to be completely removed from its shell.
When the binding energy in the orbital of the electron is less than the energy of the radiation, there will be ionization.
- Ionization: incident energy > binding energy, then the electron will be removed from the atom & the difference in energy provides the amount of kinetic energy of the ejected electron.
Quiz :Quiz True/False - During the process of excitation, electrons are removed from the atom.
True/False - Kinetic energy can be determined with information about the particular energies of electrons and the passing that is passing through.
The binding energy of an electron is 95 keV and the incident energy of radiation is 55keV.
Will there be ionization of the electron?
If the kinetic energy from a electron is 30 keV after ionizing from a source of radiation measuring 90 keV, what was the binding energy of the electron in its shell?
During excitation, is the excitement of the electron short-lived or long?
Answers to Quiz :Answers to Quiz False
True
No
60 keV
Short-lived
References :References Christian, Paul E. (2004) Nuclear Medicine and PET: Technology and Techniques.
United States: Mosby, Inc. pgs 50-51.
http://en.wikipedia.org/