Maser

Masers are used as timekeeping devices in atomic clocks, and as extremely low-noise microwave amplifiers in radio telescopes and deep-space spacecraft communication ground-stations.

The theoretical principles governing the operation of a maser were first described by Joseph Weber of the University of Maryland, College Park at the Electron Tube Research Conference in June 1952 in Ottawa,[2] with a summary published in the June 1953 Transactions of the Institute of Radio Engineers Professional Group on Electron Devices,[3] and simultaneously by Nikolay Basov and Alexander Prokhorov from Lebedev Institute of Physics, at an All-Union Conference on Radio-Spectroscopy held by the USSR Academy of Sciences in May 1952, published in October 1954.

Independently, Charles Hard Townes, James P. Gordon, and H. J. Zeiger built the first ammonia maser at Columbia University in 1953.

This device used stimulated emission in a stream of energized ammonia molecules to produce amplification of microwaves at a frequency of about 24.0 gigahertz.

For their research in the field of stimulated emission, Townes, Basov and Prokhorov were awarded the Nobel Prize in Physics in 1964.

In 2012, a research team from the National Physical Laboratory and Imperial College London developed a solid-state maser that operated at room temperature by using optically pumped, pentacene-doped p-Terphenyl as the amplifier medium.

[13] During the early 1960s, the Jet Propulsion Laboratory developed a maser to provide ultra-low-noise amplification of S-band microwave signals received from deep space probes.

Such emission is observed from molecules such as water (H2O), hydroxyl radicals (•OH), methanol (CH3OH), formaldehyde (HCHO), silicon monoxide (SiO), and carbodiimide (HNCNH).

[16] Water molecules in star-forming regions can undergo a population inversion and emit radiation at about 22.0 GHz, creating the brightest spectral line in the radio universe.

Thus, the original acronym is sometimes modified, as suggested by Charles H. Townes,[1] to "molecular amplification by stimulated emission of radiation."

Some have asserted that Townes's efforts to extend the acronym in this way were primarily motivated by the desire to increase the importance of his invention, and his reputation in the scientific community.