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Joined 2026-09-21 Message
Incoming links: Charles Hard Townes
Ammonia maser 2026-10-18
An ammonia maser uses an ammonia molecular beam, maser state selection and a maser cavity to obtain amplification or sustained microwave oscillation. In the 1954 experiment by James Power Gordon, Herbert Jack Zeiger and Charles Hard Townes, a quadrupolar static electric field focused upper-state molecules toward the cavity and deflected lower-state molecules away. The reported ammonia inversion transition lies near .[ref]
Molecular Microwave Oscillator and New Hyperfine Structure in the Microwave Spectrum of NH3 by James Power Gordon and others. pp. 282–283, Fig. 1 and Fig. 2 caption; 23 870 Mc/sec
Maser 2026-10-18
A maser uses stimulated emission to amplify microwaves. With population inversion and feedback it can sustain a coherent wave field as an oscillator. The name abbreviates "microwave amplification by stimulated emission of radiation".[ref]
Why make molecules supply an oscillator? Their energy levels offer a reproducible frequency reference, while stimulated emission lets successive molecules reinforce one coherent wave field. In his 1964 lecture, Charles Hard Townes traced his motivation to microwave spectroscopy: resolving molecular structure required useful coherent sources.[ref]
Production of coherent radiation by atoms and molecules by Charles Hard Townes. p. 58, opening discussion of microwave spectroscopy
The interesting balance is between molecular amplification and escaping energy: even a beam with population inversion fails to oscillate if cavity losses win. This is the microwave counterpart of laser threshold. Maser history 2026-10-18
The 1955 paper by James Power Gordon, Herbert Jack Zeiger and Charles Hard Townes acknowledged Nikolay Basov and Aleksandr Prokhorov's independent proposal.[ref]
The Maser—New Type of Microwave Amplifier, Frequency Standard, and Spectrometer by James Power Gordon and others. p. 1264, Introduction and reference 2
The latter authors' theory paper states that they presented the molecular-generator possibility in May 1952, cites their 1954 publication, and separately cites the Gordon–Zeiger–Townes experimental realization. These are contributions from independent groups.[ref]Theory of the Molecular Generator and Molecular Power Amplifier by Nicolay Gennadiyevich Basov and Aleksandr Mikhailovich Prokhorov. p. 426, historical footnote and references 3–4; manuscript submitted December 10, 1954, English publication October 1956
Nobel Prize in Physics in 1964 2026-10-18
One half went to Charles Hard Townes; the other half jointly to Nicolay Gennadiyevich Basov and Aleksandr Mikhailovich Prokhorov, for quantum-electronics work leading to oscillators and amplifiers using the maser-laser principle.[ref]
The Nobel Prize in Physics 1964 by Nobel Prize Outreach. Individual official award summary: Townes one-half; Basov and Prokhorov one-quarter each; common quantum-electronics motivation.