Quote:
Originally Posted by malclocke
I think a resonance transition is just when a photon of a particular frequency is absorbed and then one of the same frequency is emitted as the electron drops back down to it's previous energy level.
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Ah, is that all? That's simple enough. When he writes something like "During the cooling stage, when the optical spectrum is strengthening, the ultraviolet – the site of the resonance transitions of the same iron peak ions that dominate the optical spectrum – suddenly becomes optically thick" I thought there was some obscure quantum relationship between UV iron ions and the FeII we are seeing in the visual.
But now I reread it, all he means is that in the UV, the Fe is being bombarded by UV wavelengths, so absorbing and re-emitting individual photons (resonance) at those same wavelengths. But up in the optical spectrum (e.g. at 5018 and similar) those same ions are emitting photons through recombination, as they absorb an electron and emit a photon and move from FeII to FeI), or through transition, as they lose a photon as they drop down an energy state.
That makes sense, as the wavelengths being pumped out by the WD are strongest at the high-energy wavelengths, UV and lower, yes?
Thanks Malc, another piece falls into place.