Eric--
The Cherenkov radiation I have seen is primarily blue. It is associated with the high energy particles emitted from spent fuel in a water storage pool and I think is associated with the slowing down of the particles in water, as you suggest. I also think it is associated with the neutrons that come from the decay of fission products. The charged particles are slowed down in a short distance. The neutrons cause the bluish glow at a distance from the source. This may also be due to scattering of the blue light which is not absorbed like red in the water. I would agree that the EM radiation that is caused by either charged particles or neutrons is broad band as you suggest. Bob Sent from Windows Mail From: Eric Walker Sent: Saturday, February 7, 2015 9:20 PM To: vortex-l@eskimo.com On Sat, Feb 7, 2015 at 1:49 PM, <mix...@bigpond.com> wrote: I have a different question altogether. How does one distinguish between Cherenkov radiation and light emitted by recombining ion - electron pairs? (Where fast particles are responsible for creating the pairs.) I believe Cherenkov radiation is broadband. I read today that it is distinguishable, nonetheless, from bremsstrahlung. In the case of bremsstrahlung you need noticeable acceleration (e.g., a bending motion or a collision), whereas Cherenkov radiation arises from constructive interference when a charged particle exceeds the phase velocity of light in a medium. So you can distinguish the two in the case of a relativistic heavy ion. In that case the trajectory of the ion will be straight (so no bremsstrahlung) but it will give rise to Cherenkov radiation. My understanding is that Cherenkov radiation is broadband because the fast particle slowly decelerates, leading the frequency at which constructive interference to change over time. Please carefully vet anything I have said here. Eric
