Maser

A maser is any amplifier that produces coherent electromagnetic waves due to stimulated emission.

Terminology

The terminology of the maser is somewhat fluid. Initially the acronym was universally given as "microwave amplification by stimulated emission of radiation," which described stimulated emission in the microwave frequencies of the electromagnetic spectrum. However, as the principle of stimulated emission has since been extended to more devices and frequencies, the original acronym is sometimes modified, as pointed out by Charles H. Townes in his Nobel Prize acceptance speech of 1964 http://nobelprize.org/physics/laureates/1964/townes-lecture.pdf.

Related Topics:
Microwave - Electromagnetic spectrum - Stimulated emission - Charles H. Townes - Nobel Prize - 1964

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Maser can therefore also be taken to mean "molecular amplification by stimulated emission of radiation," as originally proposed by Townes, on account of the fact that modern masers often operate outside the microwave portion of the EM spectrum. Molecular in this sense is meant in the sense of kinetic theory; that is, in statistical mechanics, physical chemistry and chemical physics, it is common to refer to the base element of a kinetic system as a molecule. In this sense, even monatomic collisions, for example, are molecular collisions. This should not be confused with the slightly more specific notion of bound states in chemistry and physics; though a molecule in the sense of the kinetic theory subsumes the more specific definition of, for example, covalently bonded atoms.

Related Topics:
Townes - Microwave - EM spectrum - Kinetic theory - Statistical mechanics - Physical chemistry - Chemical physics - Molecule - Monatomic - Bound states - Chemistry - Physics - Covalently bonded atoms

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In this more general definition, the optical laser becomes a type of maser, as kinetic collisions also describe the process of stimulated emission in all known optical lasers. Furthermore, lasers in all other frequencies are considered masers, such that grasers (gamma ray-lasers), xasers (x-ray-lasers), uvasers (ultraviolet-lasers), optical lasers, irasers (infrared-lasers), masers (microwave lasers), and rasers (rf-lasers), are all subsets of molecular masers. However, the term laser comes from light amplification by stimulated emission of radiation, where light in this usage means any type of EM radiation (see laser article). Thus, all masers are also lasers.

Related Topics:
Optical - Laser - Stimulated emission - Gamma ray - X-ray - Ultraviolet - Infrared - Microwave - Rf - Light - EM radiation - Lasers

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In the study of astrophysics, a maser usually refers specifically to microwave radiation.

Related Topics:
Astrophysics - Microwave

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