Radiative Transfer Radiation Trapping

Arrowsmith et al used the crossed beam reaction F+Na— NaF+Na (3 P) to study radiative transfer and electronic energy transfer (E — E, V) in the Na (3 P)-1-NajCX S ) system. Previous studies of the Na2 system have utilized high-pressure cells or heat pipes in which radiation trapping is strong and Na + Na2 collisional energy transfer dominates. Time-resolved emission, following pulsed dye-laser excitation, has been used by Husain and his coworkers in a systematic survey of the excited-state behaviour of Mg(3 Pj), Ca(4 P,), and Sr(5 Pj). Dye-laser excitation of Mg vapour at 457.1 nm resulted in the observation of slow spontaneous emission from Mg(3 P,) which... 

Energy transfer transitions of the type illustrated in fig. 35.8 can also occur radiatively wherein a photon emitted by one ion is absorbed by a second ion. This leads to radiation trapping but not to lifetime shortening. 

Brian Flannery I m willing to make a very quick stab at your question. I think everyone is convinced that the buildup of greenhouse gases traps extra infrared radiation in the atmosphere, and this could lead to a problem down the road. There are few people who aren t convinced, at least in terms of the radiative transfer issues. The deep scientific questions in climate change concern the feedbacks that may occur, and the future of forcing from human actions. Once heat is trapped, climate processes, such as clouds, ocean circulation, hydrology and moist convection can change in ways that science cannot yet predict. 

What cannot be eliminated, however, is the radiative heat transfer upward within the reactor vessel from the surface of the lower plenum debris bed. About one-half to two-thirds of all energy release within the bed would be radiated upward after bottom head dryout. Initially, the primary heat sink for this radiation would be the water trapped in the downcomer region between the core shroud and the vessel wall above the debris bed. It is the heating of this water that creates the only steam source within the reactor vessel after lower plenum dryout... 

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