Maser action

In contrast to this anti-maser action in formaldehyde, H20 and OH are observed in maser emission. Collisional or radiative pumping is thought to maintain the population inversion between the two levels. As photons pass through the cloud, they are amplified by stimulated emission of radiation. The maser emission of H20 is possibly the most unusual of the observed anomalies, both from an astrophysical and a spectroscopic point of view. This is not the place to discuss details of the various models suggested, we would refer to concentrate on some of the general features observed in the maser emission spectra. 

Both the hydrated and anhydrous forms of the chelate give a red fluorescence (characteristic of the Eu " ion) when exposed to ultraviolet radiation. Fluorescence is also shown in solution. Interest in the fluorescence behavior of europium chelates is prompted by the use of these compounds in optical maser (laser) devices. Optical maser action has been demonstrated for europium chelates derived from benzoylacetone (though not for the tris chelate reported here ). 

In one laboratory exercise, students use a radio telescope to measure the emission spectra of selected molecules in astronomical sources, such as dense clouds and old stars. Molecular hyperfme structure, classical spectral patterns of linear and symmetric top species, and maser action are investigated. Another laboratory exercise was developed where students measure the rotational spectra of HCO, HCCCN, and CH3CN in the laboratory, and determine their unique spectroscopic properties. They then use their measurements to identify these molecules in interstellar gas. 

Snitzer, E. (1961). Optial MASER action of Nd-l-3 in a barium crown glass. Physical Review Letters, 7(12), 444-446. 

The threshold condition for collective emission (superradiance) or maser action (gain in the medium exceeding the losses) is much lower for Rydberg atoms than it is for the same number density of atoms in low n states. To obtain an order of magnitude estimate for the point at which collective fects occur we estimate the amplitude of the electric dipole field E radiated by an atom at a distance corresponding to a neighbouring atom. That is, if we let L represent a linear dimension in the sample which contains N atoms,... 

With the use of a resonant cavity the threshold for collective emission is lower by the magnitude of the cavity finesse. Using a cavity finesse of a 100 or so Rydberg maser action on sodium has been observed. In this case the field ionisation signal was used to monitor the population as a function of time for the states 27S, 26P and 25P corresponding to transitions An = 1 at X = 1 470 mm and An = 2... 

ABSTRACT. Interstellar molecular lines have produced spectacular examples of non-equilibrium excitation, culminating in strong maser action of 0H,Si0,H20 and CHoOH. Within the past 10 years it was recognized that maser emission is associated with star formation. 

The interstellar molecular radiation is received predominantly from sources within our Galaxy, although extremely strong maser action as well as thermal molecular radiation has been detected from many other galaxies. Thus most of the interstellar radiation we receive with our telescopes today has begun its travel towards the earth long before this beautiful University of Coimbra was founded almost 700 years ago. 

The four molecules OH, SiO, H2O, and CH OH show in one or more transitions extremely strong maser action. Only very recently has methylalcohol been added to the list of strong maser molecules (Batrla et al. 1987). Its intensity rivals that of the well known OH or H2O masers. For the observational studies of star formation OH, H2O and CH OH masers are well suited. Probably with the one exception of the source Orion A SiO masers occur in red giants and supergiants. Fig. 3 shows a series of SiO spectra towards Orion A which reveal the complex structure within the double-peaked line profiles and their time variation. 

Onsala in 1973. The water molecule H2O, which lias an angle of 105° between the H atoms, has a complex rotational spectrum. Litense maser action has been observed for the 22 GHz transition, wliich is also seen in atmospheric absorption (Fig. 7.24). High-frequency radio astronomy observations have to be performed on dr y days. A large number of other molecules, some of them quite complex, have been observed in space. The (very) remote sensing of the physical conditions in the interstellar clouds has been discussed in [7.93-7.95]. 

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