Molecular beam masers

Abstract

The purpose of this article is to review some of the developments and achievements of molecular beam masers from the time of their conception to the present and to delineate areas of particular interest and activity.A discussion of the early history of molecular beam masers is followed by an outline of the general principles and methods of preparation and use of emissive molecular beams. I n particular, electrostatic methods of state selection of molecules and maser cavity resonators are discussed in some detail.An outline of the theory of molecular beam masers is then presented with reference to a number of specific problem areas. The technique of beam maser spectroscopy is discussed with emphasis on spectral resolution and problems of sensitivity. Molecules studied by beam maser spectroscopy are tabulated and discussed. The noise, gain-bandwidth and saturation characteristics of beam maser amplifiers are reviewed. The properties of beam maser oscillators are outlined, which include oscillation conditions, noise, amplitude and frequency characteristics and transient behaviour.The paper concludes with a brief discussion of future trends.

Candidate Materials as Gain Media in Organic, Triplet-Based, Room-Temperature masers Targeting the ISM Bands

“…For the traditional gas or molecular masers, the modes that yield microwaves, either through conformational changes as in ammonia or spin states as in hydrogen [30], are inherently stable and require only physical separation to maintain stable population inversion. However, the population of molecules in the quantum state of interest is relatively low [33]. They also require high vacuum to prevent gas scattering collisions [28,30,33].…”

“…However, the population of molecules in the quantum state of interest is relatively low [33]. They also require high vacuum to prevent gas scattering collisions [28,30,33]. With a high vacuum, however, the gas molecules are spatially separated to such an extent that effective stimulation is limited, and the power output of gas-based masers is relatively low (pico to nanowatts) [33].…”