Positron

Positron - Definition and Charge of Positron

Introduction:


A positron or antielectron is the antimatter counterpart to an electron. A positron has the equal or same mass as an electron and a spin of 1/2, but it has an electrical charge of +1. When a positron collides with electron annihilation occur which results in the production of two or more gamma ray photons.

Positron is also known as the positive electron, it is positively charged subatomic particle having the same or equal mass and magnitude of charge as the electron and creates the antiparticle of a negative electron.



What is an electron?

The electron is an elementary particle that plays a vital role in the branches of science and in everyday life. The electron was first discovered by the English physicist Joseph John Thomson in 1897. An electron is a negatively charged subatomic particle. It can either be free or bound to the nucleus of an atom.

Electrons in atoms exist in spherical balls or various radii, representing the energy levels. The larger the spherical shell, the higher will be the energy contained in the electron.



Difference between electron and positron:

Both the electrons and positrons are beta β particles. A positron is the antimatter counterpart or doppelganger of an electron β-. A positron is a positive electron beta plus β+.

Positron emission gives a new nucleus with the same mass number but an atomic number that is less than the old one. 

Electron emission grants an atomic number that is one greater.

Beta emission is a process in which a nucleus emits a β particle may be a positron or an electron. This allows the atom to get the optimal ration of protons and neutrons.

There are two types of β emission:

The emission of an electron is β- decay and the emission of the positron is β+ decay.

What is positron made up of?

The positron or positive electron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1, a spin of ½ and has the same mass as an electron.

Positron and electron collide:

During the beta plus decay, a proton is converted into a neutron and a positive beta particle or beta plus. This is called a positron and it is positively charged and has the same mass. When the electron and positron collide an annihilation, event occurs, and gamma rays are produced.

Beta plus decay:

Beta plus decay is caused because a nucleus has too low a neutron: proton ratio to be stable.

Beta plus decay is a process in which a nucleus emits a positron. A positron is the antimatter counterpart or doppelganger of an electron.

Most nuclei are unstable if the neutron-proton ration is less than 1:1 for small nuclei or 1.5:1 for larger nuclei. That is, there are too many protons.

One way for the nucleus to become more stable is by the beta plus decay. This increases the number of neutrons and decreases the number of protons.

Symbol of positron:

Positron emission or beta plus decay or β+ decay is a subtype or alternate of radioactive decay called beta decay, in which a proton inside a radionuclide nucleus is converted into neutron while releasing a positron and an electron neutrino. Positron emission is mediated by the weak force.

In other words, the positron emission occurs when a proton in a radioactive nucleus changes into a neutron and release a positron and electron neutrino.

Explanation:
A positron is a type of beta particle β+. Most nuclei are unsteady or unstable if the neutron-proton ratio is less than 1:1 that is if there are too many protons. They will decay to correct the imbalance.

Positron emission increases the number of neutrons and decreases the number of protons, making the nucleus more stable or balanced. In positron emission, the atomic number Z decreases or lessens by one while the mass number A remains the same.
Magnesium-23 has 12 protons and 11 neutrons. The neutron: proton ratio is 11:12 or 0.92:1. It undergoes positron emission to form sodium-23.

How does positron emission mammography work?

Positron emission mammography works on the basis that cancer cells show an increased usage of glucose. A positron emission scanner is basically a miniature X-ray machine and a PET scanner.

Isotopes like F-18 are positron emitters. Substances consist of these isotopes collect in disease site in the body.



The patient receives a solution of F-18 fluorodeoxyglucose, which accumulates the cancer cells.

When F-18 decays, it emits a positron and a neutrino. 




The positron soon meets an electron in the tissue. They annihilate each other, producing two antiparallel 511 keV y-rays.
The PEM uses a pair of detectors place above and below the breast and mild breast compression to detect the y-rays. The signals are amplified or strengthened, and a computer uses these to generate images of thin slices through the breast. The images are then overlaid with an ordinary X-rays image.

What elements undergo positron decay?

Positron emission or beta plus decay are an appropriate type of radioactive decay, in which a proton inside a radionuclide nucleus is transformed into a neutron while releasing a positron and an electron neutrino. The positron is a type of beta particle β+, the other beta particle being the electron β- emitted from the β negative decay of a nucleus.

Isotopes which undergo this decay and thereby emit positrons are

Carbon -11, potassium-40, oxygen-15, aluminium-26, nitrogen- 13, sodium-22, fluorine-18, and iodine-121.

Positron decay is an exponential process. During radioactive decay, an unstable or changeable nucleus loses energy by emitting ionizing radiation. This radiation includes energetic alpha particles, beta particles, and gamma particles.

In any radioactive decay, it is impossible to conclude when a particular atom will decay. The chance that a given atom will decay is consistent over time.

Positron emission, therefore, follows the augmented rule for radioactive decay:
N=N0eβ^-kt.

Natural production of positron:

The positrons are naturally produced in β+ decays of occurring naturally radioactive isotopes and in interactions of the gamma with the matter. The discovery of the positive electron or positron by Anderson was the first evidence of these particles symmetrical or the particles of our everyday life. They belong to what is called the antimatter.

To demonstrate the existence of the antiproton, the scientist had to wait for the development of large particle accelerators. In 1955, the group of members’ segro, owen, using a bevatron, proved the existence of the antiproton and then shortly the antineutron.

The positron does not exist in the environment. It is possible to produce positrons with the energy greater than 511Kev, the mass of the electron or positron. One should create simultaneously one antiparticle, either a neutrino or an electron. The total electric charge will be conserved during the process.

Some of the positrons are generated by a rare type of radioactive decays, beta-plus decays. The positron is produced together with an invisible electron-neutrino that escapes detection. Energy is appropriated from the energy released in the decay.
A second process in the production of an electron and a positron during the interaction of an energetic gamma with a nucleus. As an electron is also produced 511 Kev should be added to the 511 Kev that is needed to create the positron: the gamma energy should be larger than 1022 Kev.

Few of the gammas in radioactive decays have such energies. Pair production plays a marginal role in the environment.
Every kilogram of the matter in the world contains billions of billions of billions of electrons. If it does not travel or move in a vacuum, a positron quickly encounters one of these electrons. When the positron and electron meet, which are antiparticles of each other, they destroy themselves mutually and they annihilate. 

Two annihilation of gamma with equal energy is also emitted back to back. They carry each 511 Kev that is the mass-energy of the two particles electron and positron which is thus restored. Moving in the midst of its countless electron enemies, positrons are virtually absent from the environment. These happen to be antiprotons. 

β beta decay weak forces:


The first theory of beta decay was formed in 1934 by the great Italian physicist Enrico Fermi
The forces which allow a nucleus to emit or transmit beta electrons:

Beta decay (β) changes the composition of the protons and neutrons in a nucleus. The electric charge of the nucleus will be increasing or decreasing by one. The variation of charge is compensated by the emission of a charged particle- a positron or an electron or rarely the capture of an electron. 

The main forces at work in the nucleus, those attractive that maintain its coherence and those repulsive between electric charges of the same sign are unable to transform neutrons into protons and produce electrons, positrons, antineutrinos, and neutrinos. The third type of cooperation or interaction is used by the nature to allow and proceed with beta decay or electron capture.

The third interaction is considered weak as beta decays that are most visible manifestation are very slow transformations that happen rarely. The lifetimes of unstable nuclei are extremely variable that is quarter of an hour for a free neutron, one week for iodine-131, thirty years for cesium-137, a billion years for potassium-40, but all these periods including the quarter of an hour of the neutron are very long for the nuclear block.