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What is pair production?
Pair production is the transformation of electromagnetic energy into matter, into a particle and its antiparticle, usually an electron and a positron. Let's have a look at this situation. When a high energy gamma ray with a minimum energy of 1.022 MeV passes close to an atomic nucleus, a phenomenon called pair production can occur. In this event, the energy of the gamma ray is converted into mass. It's a play right out of Albert Einstein's quantum mechanical playbook. The electron and positron are opposites of each other, and the appearance of an elementary particle and its antiparticle must obey conservation laws. That's where the "assistance" of a nearby atomic nucleus comes in. The electron and positron will appear and come away from the event with some given kinetic energy, and will scatter and slow down as they move off. The positron, of course, will end up combining with an electron in a mutual annihilation event where the two particles have their mass entirely converted into energy. This will result in a pair of electromagnetic rays, or photons, leaving the annihilation event and moving in opposite directions.
The collision of one electron and one positron produces one or two photons?
This supposition is not true. Mutual annihilation, which occurs when a positron combines with an electron, will result in the conversion of all of the mass of both particles into energy. And this will result in the formation of two photons. The production of the photon pair is the result of conservation laws, and the two photons leave the event in opposite directions. Use the related link below to learn more.
The emission of a positron also results in the creation of a?
When an atomic nucleus releases a positron, it has undergone beta plus decay. This nuclear transformation event also will release a neutrino. Use the link below for more information.
What is the minimum energy released in annihilation of electron positron pair?
Both positron and electron are of equal mass i.e about 9.1*10^-31 kg . The speed of light is about 3*10^8 m/s, and as per Einstein's theory E=m*c*c . Total mass = 2*9.1*10^-31 and c*c = (3*10^8)^2 = 9*10^16. So, energy released = 2*9.1*10^-31*9*10^16 = about 1.637*10^-13 joules, or about 1.02 MeV.
What is a positron?
A positron is a positively charged electron. It's an antielectron - antimatter! The positron has a charge of +1 (just the opposite of the -1 of the electron), and a spin of 1/2 as an electron does. The mass of this elementary particle is about 9.103826 x 10-31 kg. The actual charge on this particle is about +1.602 x 10-19 coulombs. We write it as β+ or e+ in nuclear equations. It was Paul Dirac who first theorized that it may exist back in 1928, and in 1932, Carl D. Anderson discovered and named the positron. How was it done? By allowing cosmic rays to pass through a cloud chamber shielded with lead and set up in a magnetic field, the electron-positron pairs that were sometimes created could be observed. Once created, the particles moved (curved) in opposite directions within the magnetic field. Simple and clever! It should be noted that Caltech graduate student Chung-Yao Chao is credited with detecting the positron in 1930, but he was unable to explain it. We should also note that the positron is emitted (positron emission) in beta plus decay, which is a form of radioactive decay. Pair production, the "conversion" of electromagnetic energy into a positron and an electron, is also a source of positrons. Regardless of the source, the positron will always seek to "combine" with any nearby electron with the mass of both particles being converted into electromagnetic energy (a pair of gamma rays). A more detailed description and some of the other characteristics of the positron can be found in the Wikipedia article on that subject. A link is provided below to that post and also to some Related questions that will aid in understanding this critter.
Why you need 1.022 Mev in pair?
Pair production can only occur if the energy of the photon is bigger than the rest mass (E0 = m0*c^2) of electron and positron, because this is the energy needed to create these particle (conservation of energy). Excess energy will be kinetic energy of the electron and positron. Rest mass of electron and positron is 0.511 MeV each, so 1.022 MeV in total.
How is energy turned to mass What is an example of turning energy to mass?
Energy can be turned into mass through the process of pair production, where a high-energy photon creates a particle-antiparticle pair. An example of turning energy into mass is when a gamma-ray photon interacts with an atomic nucleus, leading to the production of an electron-positron pair.
What is pair production?
Pair production is the transformation of electromagnetic energy into matter, into a particle and its antiparticle, usually an electron and a positron. Let's have a look at this situation. When a high energy gamma ray with a minimum energy of 1.022 MeV passes close to an atomic nucleus, a phenomenon called pair production can occur. In this event, the energy of the gamma ray is converted into mass. It's a play right out of Albert Einstein's quantum mechanical playbook. The electron and positron are opposites of each other, and the appearance of an elementary particle and its antiparticle must obey conservation laws. That's where the "assistance" of a nearby atomic nucleus comes in. The electron and positron will appear and come away from the event with some given kinetic energy, and will scatter and slow down as they move off. The positron, of course, will end up combining with an electron in a mutual annihilation event where the two particles have their mass entirely converted into energy. This will result in a pair of electromagnetic rays, or photons, leaving the annihilation event and moving in opposite directions.
Why conversion of a photon to an electron positron pair is not possible in free space?
Because energy mass conservation will not be satisfied in free space, so that this process needs some material by which this conversion will be proceed.
What is the minimum gamma ray energy needed to produce a positron?
The minimum photonic energy required to create an electron-positron pair is 1.022 MeV. This energy is the equivalent of the rest masses of the pair of particles created. There is a bit more to this, as conservation of momentum must be observed. Pair production will occur, when it occurs, in the vicinity of an atomic nucleus when a high energy gamma ray zips in. The nucleus provides some "help" to "balance the equations" that describe the event, and that atomic nucleus will allow symmetry to be preserved. Specifically, that atomic nucleus acts in the conservation of momentum. That's why pair production won't occur as gamma rays are flying through the vacuum of space; there are (virtually) no atoms out there to facilitate the event. It may sound complex, but it's not all that difficult to get a handle on the phenomenon. A link is provided to our friends at Wikipedia. Knowledge there is free, and pair production isn't all that tough to understand. The article is brief and readable, and the complex equations that might have been posted are absent. Check it out.
Why is it that sometimes when a very high energy electron hits a target material a positron and two or more electrons come out of the event?
An electron at high energy entering into a scattering event will bring all that energy with it. All that energy will have to be "dealt with" in the outcome. One way that a big chunk of it can be "handled" is almost magical. A large portion of the energy can be transformed into an electron-positron pair. This event is called pair production. We usually see it when a high energy gamma ray causes it, but it can be one of the outcomes in an energetic electron collision. The production of this pair of particles is the direct result of the conversion of energy into matter, and it will carry off a lot of the energy in the event. The minimum energy need to create the pair is 1.022 MeV. The original electron is still "in one piece" after the event, so it may look like the single electron crashed into a target and two electrons and a positron came away. It was actually the original electron and that electron-positron pair. If the original electron ionized another electron (or more) in the target material (which is possible), they will come away as well. Certainly there are a number of possible outcomes in an energetic electron scattering event, but pair production is one of the possible outcomes, depending on the energies involved and the target material.
What are some queries about the annihilation process that is given in Wikipedia and Google?
First of all to discuss the definition of annihilation on the Google page. The definition goes as "the conversion of matter into energy, especially the mutual conversion of a particle and an antiparticle into electromagnetic radiation." Here the matter is converted into energy. The matter is converted into energy as per the equation of the Einstein. That means E = m c 2. Here 'c' is the speed of light. That is about 300,000,000 meters/second. The "c" square becomes 90,000,000,000,000,000. So you take the electron as a unit. From this you get 90,000,000,000,000,000 times units of energy. Here you are getting only two gamma rays after collision of the electron and positron pair. That means that from the pair of gamma rays, you should be able to get one electron and one positron. That is very funny. The speed of the electron and positron is about 1 % of that of light. Now the mass-energy must be conserved. So here goes the equation. E = m 1 * 1/100 c * 1/100 c + m 2 * 1/100 c * 1/100 c = gamma ray + gamma ray. Here m 1 is the mass of electron. m 2 is the mass of positron. m 1 = m 2. So E = 2 m * 1/10000 c 2 = 2 gamma rays. Then you get m * 1/10000 c 2 = gamma ray. Gamma ray has got the speed of light. This equation gives the mass of 10,000 photons in gamma rays to be equal to one electron or one positron. That is not correct. Electron is far many times more massive than the photon. In fact the photon is presumed to have zero rest mass. That is also correct that the momentum of the system has to be conserved. Here the equation for the momentum is p = m*v. Here the mass m is equal and same in case of electron and positron. So the equation is p = m * 1/100 c. In case of electron and positron the m is equal and v is equal to 1/100 c. ( c being speed of light.) The gamma ray has got the v equal to the speed of light. Here 100 photons in gamma rays become as massive as electron or positron. That is not correct. Electron or positron are far more massive than photon. In fact the photon is presumed to have zero rest mass.The fact is that electron and positron disappear into nothing. The kinetic energy that is carried by the electron and positron can not be annihilated and is released as pair of gamma rays.The proton and anti-proton is 1836 times as massive than electron or positron. When you put this value in the E = m c 2. Then the energy produced from proton and anti-proton is 1836 times as much as produced from the electron or positron. Here as per the annihilation chapter in Wikipedia, you are getting only 9 to 13 gamma rays. This is not correct and logical. I do not get into detail of this calculations. I am not good at calculations. Only thing I want to point out that you get only two gamma rays from from pair of electron and positron is far much underestimate.Now here goes the theoretical calculation. You convert the entire mass of the universe into energy as per the equation of the Einstein. The equation goes as E = m c 2. So the unit mass will be converted into 90,000,000,000,000,000 units of energy. That is enormous quantity of energy. All the mass is converted into gamma rays. Then from every two gamma rays you get a pair of electron and positron. From 9 to 13 pair of gamma rays you will get the pair of protons and anti-proton and pair of neutrons and anti-neutron.You just calculate the amount of mass that will be produced in the process. It will be enormously high quantity of the mass than the original mass of your universe. There is equal amount of mass of anti-matter. All this newly produced mass can be reconverted into energy again. Again you can get matter and anti-matter from this energy. You can do this cycle end number of times. You can go on creating much more and more mass.Another question is why the conversion of positron and electron into gamma rays is not reversible? That is against the inter conversion of mass and energy. As per the equation of the Einstein, that is E = to m c 2, mass and energy are inter convertible. Energy can be converted into mass and mass can be converted into energy, end number of times. In case of the atomic energy the amount of energy from the mass is enormously high.So equal quantity of matter and anti-matter is produced from nothing and disappear into nothing.here goes the link.What_is_the_theory_of_creation_of_the_matter_and_anti_matter_from_nothing
What is the minimum energy to produce ionization?
The minium required energy of a photon that is involved in the creation of an electron-positron pair (which is pair production), is 1.022 MeV.An electron-positron pair has a given probability of being produced when a photon of the stated energy (or a higher energy) passes close the nucleus of an atom. Pair production does not happen "in the presence of a photon" but happens as a direct result of the the actual presence of a photon (having at least the stated energy) in the presence of an atomic nucleus. The presence of an atomic nucleus is necessary to insure conservation of the quantum mechanical characteristics of the event. Said another way, the high energy photon alone cannot spontaneously create the electron-positron pair in pair production. A link can be found below to related questions.
The collision of one electron and one positron produces one or two photons?
This supposition is not true. Mutual annihilation, which occurs when a positron combines with an electron, will result in the conversion of all of the mass of both particles into energy. And this will result in the formation of two photons. The production of the photon pair is the result of conservation laws, and the two photons leave the event in opposite directions. Use the related link below to learn more.
The emission of a positron also results in the creation of a?
When an atomic nucleus releases a positron, it has undergone beta plus decay. This nuclear transformation event also will release a neutrino. Use the link below for more information.
What is the minimum energy released in annihilation of electron positron pair?
Both positron and electron are of equal mass i.e about 9.1*10^-31 kg . The speed of light is about 3*10^8 m/s, and as per Einstein's theory E=m*c*c . Total mass = 2*9.1*10^-31 and c*c = (3*10^8)^2 = 9*10^16. So, energy released = 2*9.1*10^-31*9*10^16 = about 1.637*10^-13 joules, or about 1.02 MeV.
If a photon is the product of the Dirac annihilation energy of a virtual electron-positron pair how is the energy dispersed?
In mutual annihilation, a positron and an electron combine. and the masses of both particles are entirely converted into energy. The energy is divided between not one but two gamma rays, each moving in the opposite direction. Only the two photons are produced in this phenomenon, and all quantum mechanical characteristics must be conserved. Additionally, the use of the term "virtual" to describe the electron-positron pair is probably something that might be avoided.We might note that the mutual distruction of an electron-positron pair is called mutual annihilation by physics types. A separate question (and its answer) exist. There is a bit more to this as regards the aspects of conservation, but the essential ideas are all contained here. Use the links below for more information.
