POSITRON EMISSION Meaning and
Definition
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Positron emission, also known as beta plus decay, is a radioactive decay process in which a positron, a subatomic particle with the same mass as an electron but a positive charge, is emitted from an unstable atomic nucleus. It occurs when there is an excess of protons over neutrons in the nucleus, causing it to become unstable and undergo radioactive decay.
During positron emission, a proton in the nucleus is converted into a neutron, releasing a positron in the process. The positron is then ejected from the nucleus and travels through the surrounding material until it encounters an electron. Upon collision, the positron annihilates with the electron, converting their combined mass into energy in the form of gamma rays. This annihilation process results in the complete destruction of both particles, effectively "canceling out" the positive and negative charges.
Positron emission is commonly observed in certain radionuclides, particularly isotopes that have an excess of protons. It is a form of natural transmutation, where one element is transformed into another due to the emission of a positron. This decay process has various applications in medical imaging techniques such as positron emission tomography (PET), where positron-emitting radionuclides are introduced into the body to track metabolic processes and detect abnormalities.
Overall, positron emission is a fundamental mechanism of radioactive decay, playing a crucial role in the understanding of particle physics and finding practical applications in the field of diagnostic imaging.
Etymology of POSITRON EMISSION
The term "positron emission" can be broken down into two parts: "positron" and "emission".
1. Positron: The word "positron" is derived from the Latin word "positus", which means "placed" or "put". It was coined in the early 1930s by physicist Paul Dirac, who proposed the existence of a positively charged electron or antielectron, to explain the symmetrical behavior of matter and antimatter. Dirac combined the Latin word "positus" with the electron to create the term "positron".
2. Emission: The word "emission" comes from the Latin word "emissus", which means "sent out" or "dismissed". In the context of positron emission, it refers to the process by which a positron is emitted or released from an atomic nucleus during radioactive decay.
