Fr.: maser à ammoniac, ~ NH3
A maser source in which excited → ammonia molecules (NH3) produce → maser emission. The first device to demonstrate the principle of → stimulated emission of radiation used ammonia molecules (Gordon et al. 1954). The hydrogen atoms of ammonia molecules have a rotation motion whereas the nitrogen atom oscillates between two positions, above and below the plane of the hydrogen atoms. These arrangements do not represent exactly the same energy, and therefore the molecule exists in two energy states. The difference in energy between the states corresponds to a frequency of 23.87 GHz, or 1.25 cm. In astrophysics, ammonia maser emission has been detected toward active star formation regions, such as W51. → interstellar masers.
Fr.: maser circumstellaire
Maser emission from molecules in the circumstellar envelopes of → red giants, and also from regions around → protostars.
→ circumstellar; → maser.
Fr.: maser interstellaire
A maser phenomenon created by young stars and → protostars in the surrounding dense → molecular clouds of gas and dust. See also → circumstellar maser; → ammonia maser; → methanol maser; → OH maser; → water maser.
→ interstellar; → maser.
1) A source of very intense, narrow-band, coherent microwave
radiation involving → stimulated emission, as
in the → laser.
Maser stands for Microwave Amplification by Stimulated Emission of Radiation; → laser.
gosil-e meyzeri (#)
Fr.: émission maser
An emission arising from the → maser process.
Fr.: maser méthanol
A maser source in which excited methanol molecules (CH3OH) produce → maser emission. Methanol masers are signposts of the early stages of star formation, many being associated with sources that have not developed an → H II region. There are more than 20 different methanol transitions that have been observed. They are divided into two categories: Class I, excited by collisions, and class II, excited by infrared radiation. The most important class I masers are at a frequency of 44.1 GHz, while he most important class II masers are at a frequency of 6.7 GHz.
Fr.: maser OH
A → maser phenomenon created by → OH molecules with characteristic → OH lines. OH masers are detected toward a variety of astronomical environments, including massive star formation regions and evolved late-type stars.
Fr.: maser H2O
An interstellar → maser phenomenon in which water (H2O) molecules undergo the processes of → population inversion and → stimulated emission. H2O masers are detected toward star formation regions and the envelopes of evolved stars. The maser emission comes from regions that are typically quite small, not larger than the solar system. The main emission frequency is 22 GHz, which shows up in strong lines. There are, however, other H2O maser transitions at 380 GHz and 183 GHz, which are much weaker than the 22 GHz line. The former transitions are sporadically detected since they are strongly absorbed in the Earth's atmosphere, because of its high water vapor content.