Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Physics

Supervisor

Prof. Martin Houde

Abstract

It is generally assumed that in the interstellar medium much of the emission emanating from atomic and molecular transitions within a radiating gas happen independently for each atom or molecule, but as was pointed out by R. H. Dicke in a seminal paper several decades ago this assumption does not apply in all conditions. As will be discussed in this thesis, and following Dicke’s original analysis, closely packed atoms/molecules can interact with their common electromagnetic field and radiate coherently through an effect he named superradiance. Superradiance is a cooperative quantum mechanical phenomenon characterized by high intensity, spatially compact, burst-like features taking place over a wide range of time-scales, depending on the size and physical conditions present in the regions harbouring such sources of radiation. I will discuss the potential for superradiance in the atomic hydrogen 21-cm line for which we extended Dicke’s analysis to the magnetic dipole interaction characterizing this line. Then, the application of superradiance to the OH 1612-MHz, CH3OH 6.7-GHz and H2O 22-GHz maser lines will be discussed, and it will be shown that super-radiance provides a valid explanation for previous observations of intensity flares detected in these spectral lines for some astronomical sources. An interesting result is that superradiance provides a natural mechanism for the recent observations of periodic and seemingly “alternating” methanol and water flares in G107.298+5.639 that cannot be easily explained within the context of maser theory.

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