Maser Action in Methanol Transitions

There is a large body of evidence to suggest that the anomalous OH emission sources—particularly those which are classified as class I sources—are associated with protostars. It is also known, from the theories brought forward over the past four years, that maser action can be caused by quite a variety of non-equilibrium situations. It is argued here that one particular kind of non-equilibrium situation which can plausibly be expected to exist in protostars is very similar to that proposed previously in the electron-pumping model, and that, in this new context, it can mimic most of the observed features of class I sources.

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Molecular spectroscopy prompted by astrophysical observations

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1981.0224 ◽

1981 ◽

Vol 303 (1480) ◽

pp. 551-563 ◽

Cited By ~ 2

Keyword(s):

Molecular Spectroscopy ◽

Far Infrared ◽

Molecular Spectra ◽

National Bureau ◽

Millimetre Wave ◽

The Galaxy ◽

Wave Region ◽

Simple Molecules ◽

Basic Level ◽

Maser Action

Observations of molecules in the Galaxy, whether by absorption, spontaneous emission or maser action, have shown that for all that molecular spectroscopy has long been studied in great detail, there are large gaps in our knowledge of even simple molecules, both in general and in detail. At the most basic level, a number of unidentified radio frequency lines were detected some while ago, and with the extension of observations into the millimetre wave region, many more unidentified lines have been found. Despite earlier extensive work at the National Bureau of Standards of the U. S. A, there remains a great need for measurements of frequencies of transitions in many molecules. The fact that galactic concentrations of molecules are often associated with strong sources of far infrared or ultraviolet radiation has shown that there are many gaps in our knowledge of molecular spectra in those technically difficult ranges of the spectrum and has led to attempts to develop improved techniques for studying them, as well as to interest in some theoretical problems.

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UV Absorption Spectra of Molecules and the Connection with Pumping Mechanisms for Astrophysical Masers

International Astronomical Union Colloquium ◽

10.1017/s0252921100120044 ◽

1977 ◽

Vol 43 ◽

pp. 6-6

Author(s):

J.C. Viney

Keyword(s):

Interstellar Medium ◽

Absorption Spectra ◽

Theoretical Models ◽

Uv Absorption ◽

Uv Absorption Spectra ◽

Physical Mechanisms ◽

Brightness Temperatures ◽

Wide Acceptance ◽

Important Region ◽

Maser Action

Since interstellar masers were first discovered in 1965, various attempts have been made to account for the variety of behaviour observed. In particular a number of theoretical models have been advanced to account for the pumping mechanisms but none have gained a wide acceptance.Over forty molecules have now been identified in the interstellar medium, of these five exhibit maser action; they are detected by virtue of their small angular diameter and very large brightness temperatures > 1013°K. The molecules in question are H20, OH, SiO, CH3OH and CH, of these the Hydroxyl maser presents the widest range of behaviour and therefore if the physical mechanisms involved could be understood these masers could be used to probe the interstellar environment and obtain more information about this important region where new stars are formed

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Λ-Doublet Population Inversion in Collisions of OH, OD, CH, CD and NH+

Symposium - International Astronomical Union ◽

10.1017/s0074180900073290 ◽

1980 ◽

Vol 87 ◽

pp. 583-587 ◽

Cited By ~ 1

Author(s):

R. N. Dixon ◽

D. Field

Keyword(s):

Qualitative Agreement ◽

Scattering Theory ◽

Population Inversion ◽

Closed Shell ◽

Inelastic Collisions ◽

The Other ◽

New Approach ◽

Maser Action

The results of a new approach to the problem of the collisional step in the pumping cycle for OH and CH masers are reported. Rotationally inelastic collisions of OH and CH with both open and closed shell collision partners are considered using an expression derived from scattering theory. It is shown how Λ-doublet population inversion may arise in OH and CH. H-atoms and H2 may show opposite behaviour with CH, one partner cooling where collisions with the other lead to inversion. Implications for maser action are discussed and reveal excellent qualitative agreement with observation. Λ-doublet population inversion in OD, CD and NH+ is also considered.

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