On Sun, Jun 1, 2014 at 10:56 AM, Bob Cook <[email protected]> wrote:
However, the MRI absorption and emission of energy may not be called EM > radiation the way you are using the term. Nevertheless MRI does entail > nuclear emission of low energy quanta IMHO I'm wading into a thread that I have no business wading into, because it is a very interesting one. Some additional thoughts to add: - Consider extremely low frequency (ELF) waves [1], which have wavelengths on the order of 5000 km. I don't think people know for sure what the mechanism for their emission is exactly, but presumably it is through the oscillation of electrons. - Electrons in an isolated atom (e.g., monoatomic hydrogen) excite and relax in quanta of energy. Because there is a conduction band in a metal, electrons in a metal excite and relax along a broadband spectrum, and presumably quantum considerations do not apply. - To my knowledge, in their excitations nuclei do not ever enter into a banded state comparable to that of electrons in the conduction band of a metal. So quantum considerations would seem to apply there. I think a point that has been made is that in a quantum emitter, the minimum delta between energy levels is perhaps what determines the maximum wavelength of the nuclear emitter. In this case it would seem to be the excitation profile of the emitter and not the geometry, per se, that is the determining factor. (All of this discussion is apart from the interesting point about precession of nuclei, e.g., in MRI.) I assume that the main thing going on with nuclei is the rearranging of nucleons into higher and lower energy levels, where the nucleus emits a high-pitched shriek when the nucleons snap into place in a lower energy level (this is the gamma that is emitted). Eric [1] http://en.wikipedia.org/wiki/Extremely_low_frequency
