MASERS IN SPACE

Of the seven molecules presently detected at radio wavelengths in the interstellar medium, OH and H₂O display spectacular emission properties attributed to maser action. The OH masers fall into three distinct classes, herein described, each of which is anomalously excited by a different pumping mech...

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Bibliographic Details
Published in:Publications of the Astronomical Society of the Pacific 1970-10, Vol.82 (489), p.996-1021
Main Author: TURNER, B. E.
Format: Article
Language:English
Subjects:
Cosmic dust
Ground state
Hydroxyl radical clouds
Hydroxyl sources
Infrared radiation
Main lines
Masers
Molecules
Photons
Pumping
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Summary:Of the seven molecules presently detected at radio wavelengths in the interstellar medium, OH and H₂O display spectacular emission properties attributed to maser action. The OH masers fall into three distinct classes, herein described, each of which is anomalously excited by a different pumping mechanism. Far IR radiative pumping is applied to recent observations of anomalous OH emission in dust clouds. The excitation of OH by the collisional dissociation of water vapor is described next, and is shown to explain recent observations of microwave emission from excited states of OH. It also explains why the type of OH emission that it produces (Class I) is observed to occur in the same regions as anomalous H₂O emission. A pumping mechanism for the H₂O is also described which is expected to operate in any regions in which Class I OH emission occurs.
ISSN:0004-6280
1538-3873
DOI:10.1086/128997