Hi Jacob, Concerning orbital transitions occurring around the absorption edge, in addition to the other helpful suggestions, I would suggest looking at review papers on the fundamentals of x-ray absorption spectroscopy. For example: Yano and Yachandra, Photosynthesis Research, 2009 102:241-254 clearly describes specific electronic transitions that occur at various portions of the absorbance spectrum. They also discuss how the three different L edges arise from spin-orbit coupling.
Concerning one of your later remarks, "When the atoms fluoresce, they look different to the incident x-ray beam", if a single x-ray photon enters an "unexcited" crystal is it possible for this x-ray to be scattered anomalously? Philip On Wed, Mar 11, 2015 at 12:57 PM, Keller, Jacob <[email protected]> wrote: > Dear Crystallographers, > > I have had only a vague understanding of what specific things are > happening with shell electrons at anomalous edges. Specifically, for > example, to what energy of electron-transition does the x-ray k-edge > correspond in terms of orbitals, and is that transition energy actually > equal to the energy of the photon, suggesting that the photon is absorbed > (or disappears?) in elevating the electron? I don't think we say it is > absorbed, so how does the energy come back out, from the electron's falling > back down, right? So then there's a new photon created, or the same one > comes back out? Where was it? > > Further, I also have heard that the emerging anomalous/resonance photons > are of the same wavelength as the incident radiation, but usually there is > something lost in transitions (even non-fluorescence ones) I thought? Has > it ever been definitively shown that the anomalous photons are of the same > energy as the incident radiation? > > In the case of L-edges, why are there three separate edges? Further, if > the resonance occurs when the energies are equal, why does resonance occur > at energies greater than the edge? I don't think this happens in other > resonance phenomena, or does it? If projects a middle-C-tone into a piano, > do all of the lower notes resonate as well, according to the Kramers-Kronig > relation? I think it may actually happen in the mammalian cochlea's > travelling wave, but is it completely general to resonance phenomena? > > Just interested, and have wondered these things for a long time in the > background of my mind... > > Jacob Keller > > > ******************************************* > Jacob Pearson Keller, PhD > Looger Lab/HHMI Janelia Research Campus > 19700 Helix Dr, Ashburn, VA 20147 > email: [email protected] > ******************************************* >
