Let's start with the term Gamma Spectrometry. Often, the term Gamma Spectroscopy is also used, which is not entirely correct, as we will explain later.
The term Gamma Spectrometry consists of the two terms Gamma and Spectrometry. Here, Gamma is an abbreviation for Gamma Radiation. We will take a closer look at what these two terms mean. Let's start with Gamma radiation.
Gamma Radiation
As you may already know, every material substance is made up of individual atoms. If you have a cup of coffee in front of you while you browse these pages, then this cup is likely made mainly of silicon and oxygen atoms, while your coffee consists of hydrogen, oxygen, carbon, nitrogen, and other atoms. You yourself are also made of atoms: approximately 96% of your atoms are oxygen, carbon, hydrogen, and nitrogen.
Each individual atom consists of different particles, namely protons, neutrons, and electrons. The protons and neutrons form the nucleus of the atom, while the electrons are found in the electron shell that surrounds the nucleus. The number of protons in an atom is referred to as its atomic number or nuclear charge number. This defines, among other things, the chemical properties of an atom.
You may have also encountered the term element in this context. An element is a pure substance that consists entirely of one type of atom. For example, the element carbon is made up of all atoms that have the nuclear charge number 6, which means 6 protons. The following list shows some examples of nuclear charge numbers and their corresponding element names.
List of examples of nuclear charge numbers and their corresponding element names.
| Number of Protons (Nuclear Charge Number) | Element Name |
|---|---|
|
1 |
Hydrogen |
|
6 |
Carbon |
|
7 |
Nitrogen |
|
8 |
Oxygen |
|
14 |
Silicon |
A list of all element names with nuclear charge 1 to 84 can be found here.
Note:
The nuclei of specific elements (e.g., hydrogen, carbon, ...) are referred to as nuclides.
Why have we spent so much time discussing atoms, protons, neutrons, atomic number, etc., if we want to know what the term Gamma radiation refers to?
Well, here is where the so-called radioactive decay comes into play. We also need to look at the neutrons contained in an atomic nucleus alongside the protons.
Let's start with the neutrons: We already know that an atomic nucleus is made up of protons and neutrons. The number of protons determines the element or nuclide designation. However, each element can have a different number of neutrons. For example, the element carbon can have 6, 7, or 8 neutrons. These different combinations are referred to as isotopes of the element carbon. If you add the number of protons and neutrons of an element, the resulting value is called the mass number A.
Two examples:
Schematic representation of three Beryllium isotopes with mass numbers 7, 9, and 12. The protons are depicted in red, and the neutrons in gray.
This brings us to radioactive decay: There are stable isotopes and unstable isotopes. The stable isotopes ensure that you can drink your coffee without fearing that your coffee cup will suddenly decay (unless you drop the cup yourself). In contrast, the unstable isotopes decay after a certain period. During this process, the number of protons in the atomic nucleus changes, transforming the element into another element through decay. This transformation (decay) is often accompanied by the emission of radiation, namely the aforementioned Gamma radiation.
What is so special about Gamma radiation that we are focusing on it so intensively?
One reason is that it is a electromagnetic radiation, similar to visible light. However, Gamma radiation has a much higher energy. It can penetrate materials and damage chemical or biological bonds or structures, which is why an important aspect of radiation protection is how to protect oneself from potential harmful effects of Gamma radiation, but it can also be used for many different applications (e.g., radiography, tomography, etc.). Additionally, the Gamma radiation emitted during the decay of an isotope has specific (discrete) energies that are characteristic of each isotope.
Did you read the last sentence carefully and are the implications clear to you?
If not, here is the summary:
If we can find a way to determine the energy of the Gamma radiation emitted during the radioactive decay of an isotope, then we can identify which isotope has decayed. In principle, we would then have the possibility to identify radioactive isotopes!
This conclusion brings us directly to the second term, spektrometry:
