Dicke's Superradiance in Astrophysics
Fereshteh Rajabi, University of Western Ontario
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 my presentation, 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 timescales, depending on the size and physical conditions present in the regions harbouring such sources of radiation. I will present the application of superradiance to the OH 1612-MHz, CH3OH 6.7-GHz and H2O 22-GHz maser lines where superradiance 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 explained within the maser theory.