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Prokhorov, Aleksandr Mikhailovich

Aleksandr Mikhailovich Prokhorov (əlyĬksän´dər mēkhī´ləvĬch prô´khərəf), 1916–2002, Russian physicist, b. Atherton, Queensland, Australia. In 1923 he was taken to the Soviet Union by his parents, who had emigrated to Australia to escape the czarist regime. In 1947 he began his research into the coherent radiation of electrons, followed by pioneering work in the field of radio-frequency spectroscopy. With N. G. Basov he created an oscillator based on the stimulated emission of electromagnetic waves by the excited molecules of a molecular beam. In the process of developing an ammonia-beam molecular oscillator, Prokhorov formulated the main principles of, and laid the physical foundation for, quantum electronics. For this work, which led to the construction of oscillators and amplifiers based on the maserlaser principle, Prokhorov shared the 1964 Nobel Prize in Physics with Basov and C. H. Townes.

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maser

maser (acronym for microwave amplification by stimulated emission of radiation) Device using atoms artificially kept in states of higher energy than normal to provide amplification of high-frequency radio signals. Masers are used to amplify signals from spacecrafts and as oscillators in atomic clocks. US physicist Charles Townes discovered the principle, for which he shared the 1964 Nobel Prize in physics with the Soviet physicists Nikolai Basov and Aleksandr Prokhorov. The first maser used electrostatic (charged) plates to separate high-energy ammonia atoms from low-energy ones. Radiation of a certain frequency stimulated the high-energy ammonium atoms to emit similar radiation and strengthen the signal. The principle is also applied to the laser.

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Prokhorov, Aleksandr Mikhailovich

Prokhorov, Aleksandr Mikhailovich (1916–2002) Soviet physicist, b. Australia. He shared the 1964 Nobel Prize in physics with Nikolai Basov and Charles H. Townes. Prokhorov's research in quantum electronics resulted in the development of the maser and laser.

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maser

ma·ser / ˈmāzər/ • n. a device using the stimulated emission of radiation by excited atoms to amplify or generate coherent monochromatic electromagnetic radiation in the microwave range.

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maser

maser (ˈmeɪzə) microwave amplification by stimulated emission of radiation

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maser

maser An acronym for microwave amplification by stimulated emission of radiation, a device resembling a laser but emitting radiation at microwave frequencies.

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maser

maser (mā´zər), device for creation, amplification, and transmission of an intense, highly focused beam of high-frequency radio waves. The name maser is an acronym for microwave amplification by stimulated emission of radiation, microwaves being radio waves of short wavelength, or high frequency. The maser is an oscillator in which the basic frequency control arises from an atomic resonance rather than a resonant electronic circuit. The waves produced by the maser are coherent, that is, all of the same frequency, direction, and phase relationship, while the waves produced by most sources of electromagnetic radiation are emitted in all directions over a wide range of frequencies and have all possible phase relationships. Maser radiowaves are much closer to an ideal single-frequency source than those of ordinary radio transmitters. As a result, the maser output can be transmitted over fairly large distances with relatively little loss. The principle of the maser was conceived of in the early 1950s, based on the developments of the quantum theory, and the first maser was operated in 1954 by C. H. Townes, J. P. Gordon, and H. J. Zeiger. In 1960 the first optical maser was developed by T. H. Maiman (the optical maser is now called a laser). Beginning in 1965 a number of masers have been found in space; the first such natural laser discovered lies in the Great Nebula of Orion and is driven by the hydroxyl (OH) molecule. Masers have been developed to operate at many different wavelengths, so that the original designation "microwave" is no longer strictly accurate. In the maser, electromagnetic radiation is produced by stimulated emission; an atom or molecule in an excited state (i.e., a state of increased energy) emits a photon of a specific frequency when struck by a second photon of the same frequency. The emitted photon and the bombarding photon emerge in phase and in the same direction. For such emissions to take place in sufficient numbers to produce a steady source of radiation, many atoms or molecules must first be "pumped" to the higher energy state. The first maser used molecules of ammonia gas, which oscillate at a characteristic natural frequency between two energy states. Paramagnetic ions in crystals have also been used as the source of coherent radiation for a maser. A maser may be used as an amplifier or as an oscillator, the latter application requiring a higher power level. One of the most useful types of maser is based on transitions in atomic hydrogen occurring at a frequency of 1,421 megahertz. The hydrogen maser provides a very sharp, constant oscillating signal, and thus serves as a time standard for an atomic clock.

See M. Bertolloti, Masers and Lasers (1983).

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Maser

Maser

Maser is an acronym for microwave amplification by stimulated emission of radiation. As such, it makes electromagnetic waves (specifically microwaves) through amplification due to stimulated emission. Microwaves correspond to that portion of the electromagnetic spectrum where the radiation has wavelengths of 0.039 to 12 in (1 mm to 30 cm); i.e., between the far infrared and radio frequencies. Under its now broad usage beyond just microwaves, many scientists, including its discoverer Charles Townes, has suggested that the word microwave, within maser, be replaced with the word molecular.

Crystals can be used as amplifiers of microwave radiation and as sources of radiation having a single wavelength and frequency. A maser amplifies the intensity of microwaves by taking advantage of a principle that was first discovered by American physicist, educator, and Nobel laureate Charles Hard Townes (1915). In 1953, Townes, J.P. Gordon, and H.J. Zeiger built masers, independently of one another, at Columbia University. Their work was based on the theoretical research performed by Joseph Weber, Nikolay Basov, and Alexander Prokhorov described in 1952 and, later, published in 1954. Basov, Prokhorov, and Townes were awarded the Nobel Prize in physics in 1964 for their research and work with masers.

According to quantum mechanics, electrons exist in discrete energy states. In the case of a two level system, the electrons can populate one of two energy states. There will be a certain probability of finding an atoms electron in the lower energy state, and another probability of finding an atoms electron in the lower energy state, and another probability of finding an atoms electron in the higher energy state.

When an electron drops from the higher energy state to the lower one, it emits energy. Similarly, an electron must absorb energy to be promoted from the lower energy state to the higher one. The net energy emitted by electrons traversing the two energy states thus depends on the energy difference between the two states and on the difference in populations of the two energy states.

Under conditions of thermal equilibrium, the number of atoms having electrons in the lower energy state will exceed the number having electrons in the higher energy state. If electrons are pumped into the higher energy state by exciting them with excess energy, a higher rate of energy emission will result as the electrons try to restore thermal equilibrium by returning to the lower energy state.

The central problem of the maser is to obtain a suitable excess population in the upper state, thereby stimulating the emission of microwave radiation having a single wavelength and frequency. Such radiation is said to be coherent. In practice, masing action is accomplished in various ways. Good low noise amplifiers at microwave frequencies have been made using ruby masers. These amplifiers have found application in radio astronomy and space communication.

A laser (acronym for light amplification by stimulated emission of radiation) amplifies light in a different region of the electromagnetic spectrum by the same method that the maser amplifies microwaves.

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Maser

Maser

Maser is an acronym for microwave amplification by stimulated emission of radiation . Microwaves correspond to that portion of the electromagnetic spectrum where the radiation has wavelengths of 0.039-12 in (1 mm-30 cm), i.e., between the far infrared and radio frequencies.

Crystals can be used as amplifiers of microwave radiation and as sources of radiation having a single wavelength and frequency . A maser amplifies the intensity of microwaves by taking advantage of a principle that was first discovered by the American physicist and Nobel laureate, Charles Townes.

According to quantum mechanics , electrons exist in discrete energy states. In the case of a two level system, the electrons can populate one of two energy states. There will be a certain probability of finding an atom's electron in the lower energy state, and another probability of finding an atom's electron in the lower energy state, and another probability of finding an atom's electron in the higher energy state.

When an electron drops from the higher energy state to the lower one, it emits energy. Similarly, an electron must absorb energy to be promoted from the lower energy state to the higher one. The net energy emitted by electrons traversing the two energy states thus depends on the energy difference between the two states and on the difference in populations of the two energy states.

Under conditions of thermal equilibrium, the number of atoms having electrons in the lower energy state will exceed the number having electrons in the higher energy state. If electrons are pumped into the higher energy state by exciting them with excess energy, a higher rate of energy emission will result as the electrons try to restore thermal equilibrium by returning to the lower energy state.

The central problem of the maser is to obtain a suitable excess population in the upper state, thereby stimulating the emission of microwave radiation having a single wavelength and frequency. Such radiation is said to be coherent. In practice, masing action is accomplished in various ways. Good low noise amplifiers at microwave frequencies have been made using ruby masers. These amplifiers have found application in radio astronomy and space communication.

A laser (acronym for light amplification by stimulated emission of radiation) amplifies light in a different region of the electromagnetic spectrum by the same method that the maser amplifies microwaves.

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