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From Universe to Earth: How Does Positron Emission Reveal the Origin of Our Universe?
Positron emission, also known as β+ decay, is a decay method in which protons inside the radionuclide nucleus are converted into neutrons and simultaneously release positrons and electron neutrinos. This process occurs through weak interactions, and when the number of protons is reduced, it causes the element in the nucleus to transform, forming an element with a mass number reduced by one.
Positron emission is key to understanding the universe because it involves not only the behavior of elementary particles but also helps scientists understand broader cosmic phenomena.
In nature, positron emission is rare and is only observed in the decay of certain isotopes and cosmic ray interactions, such as potassium-40. On Earth, this rare isotope of potassium accounts for only 0.012% of potassium, and its probability of emitting positrons is only one in 100,000. Positron emission is different from electron emission or beta-decay, which is the conversion of neutrons into protons and the release of electrons and antineutrinos.
Historical discovery of positron emission
The history of positron emission dates back to 1934, when Frederic and Elaine Curie observed nuclear reactions by bombarding aluminum with alpha particles, creating short-lived elements. They found that the positrons given off by the gas were identical to those discovered in cosmic rays by Carl Anderson in 1932, considered the first example of beta+ decay. This discovery earned them a Nobel Prize.
Positron-emitting isotopes
Many isotopes emit positrons, including carbon-11, nitrogen-13, oxygen-15, fluorine-18, etc. These isotopes are widely used in medical imaging technology such as positron emission tomography (PET). For example, when carbon-11 decays into boron-11, positrons and neutrinos are released.
Positron emission tomography (PET) is revolutionizing medical imaging, allowing doctors to see changes in cells, tumors and other health conditions more clearly.
Mechanism and energy of positron emission
Behind the emission of positrons is the behavior of elementary particles, quarks, which can change species through weak interactions, turning protons into neutrons. Decay occurs when the energy is suitable to produce positrons. However, when the parent nucleus is not massive enough to support this process, positron emission cannot be activated. This makes the stability of mental substances an important part of physics.
Applications and future prospects
The applications of positron emission are not limited to basic science, but also extend to the medical field. Use short-lived positron radioactive isotopes such as carbon-11 (which has a half-life of 20.4 minutes) and fluorine-18 (which has a half-life of 110 minutes), which are widely used in medical imaging technology. Positron emission tomography uses the energy released by these isotopes to generate high-definition medical images.
Finding the key to understanding how we exist, perhaps positron emission can help unlock the profound shackles of the universe.
Positron emission is not only an important part of physics, but the mysteries of the universe it reveals also provide endless possibilities for mankind to explore the unknown. Can this change in the microscopic world further reveal the origin and destiny of our universe?
