Quoting Jacob Keller :
Also, in your selenium crystal example, I think there would still be an
anomalous signal, because there would always be regular scattering as
well
as the anomalous effect. Isn't that true?
It is certainly not correct to state that there is no anomalous
scattering in
Quoting Jacob Keller :
Also, in your selenium crystal example, I think there would still be an
anomalous signal, because there would always be regular scattering as well
as the anomalous effect. Isn't that true?
It is certainly not correct to state that there is no anomalous
scattering in
Quoting Jacob Keller :
Aha, so I have re-invented the wheel! But I never made sense of why f' is
negative--this is beautiful! Just to make sure: you are saying that the real
part of the anomalous scattering goes negative because those photons are
sneaking out of the diffraction pattern through a
Jacob Keller wrote:
Dear Dr. Holton and CCP4BBers,
Are you saying that a resonant event is always accompanied by a
fluorescence event?
no.
For example, with selenium only ~59% of the core holes decay by emitting
a fluorescent x-ray. The rest by emitting an Auger electron. The
latter seldo
University
> > Medical Scientist Training Program
> > Dallos Laboratory
> > F. Searle 1-240
> > 2240 Campus Drive
> > Evanston IL 60208
> > lab: 847.491.2438
> > cel: 773.608.9185
> > email: j-kell...@northwestern.edu
> >
oratory
> F. Searle 1-240
> 2240 Campus Drive
> Evanston IL 60208
> lab: 847.491.2438
> cel: 773.608.9185
> email: j-kell...@northwestern.edu
> ***
>
> - Original Message -
> From: "Ethan Merritt"
> To: "
tern.edu
***
- Original Message -
From: "Ethan Merritt"
To: "Jacob Keller" ;
Sent: Friday, April 24, 2009 1:40 PM
Subject: Re: [ccp4bb] Reason for Neglected X-ray Fluorescence
On Friday 24 April 2009 11:28:16 Jacob Keller wrote:
Dear Dr. Holton an
On Friday 24 April 2009 11:28:16 Jacob Keller wrote:
> Dear Dr. Holton and CCP4BBers,
>
> Are you saying that a resonant event is always accompanied by a fluorescence
> event? If that were true, wouldn't the resonant event end up manifesting as
> *negative* scattering component from the resonant
-kell...@northwestern.edu
***
- Original Message -
From: "James Holton"
To:
Sent: Thursday, April 23, 2009 8:59 PM
Subject: Re: [ccp4bb] Reason for Neglected X-ray Fluorescence
Dirk Kostrewa wrote:
yes, this is certainly true for real fluorescence eff
Dirk Kostrewa wrote:
yes, this is certainly true for real fluorescence effects. But the
anomalous scattering can be best thought of as a resonance phenomenon
without any frequency change, and as such, it has a distinct phase
relationship to the elastically scattered photon and does have an
eff
For those who are still following this discussion...
Following a comment by James, I clarify my previous statement about
"the limiting case when the total mass of the crystal is very large
with respect to the mass of one photon"
I meant of course the "relativistic mass" of one photon [which i
James Holton wrote:
marc.schi...@epfl.ch wrote:
The elastically scattered photons (which make up the Bragg peaks) also
do not not retain the momentum of the incident photon.
Although technically true to say that photons traveling in different
directions have different momenta, all ela
Am 23.04.2009 um 02:31 schrieb James Holton:
Fluorescent x-rays have a VERY different wavelength from the
incident beam and therefore cannot interact coherently with Bragg-
scattered photons, so they contribute to nothing but background.
Fluorescence is also a true absorption-reemission pro
marc.schi...@epfl.ch wrote:
The elastically scattered photons (which make up the Bragg peaks) also
do not not retain the momentum of the incident photon.
Although technically true to say that photons traveling in different
directions have different momenta, all elastically scattered photons
On Wednesday 22 April 2009 13:22:41 marc.schi...@epfl.ch wrote:
> Quoting Ethan Merritt :
>
> > On Wednesday 22 April 2009 09:23:19 Jacob Keller wrote:
> >> Hello All,
> >>
> >> What is the reason that x-ray fluorescence is neglected in our experiments?
> >> Obviously it is measureable, as in EXAF
Quoting Ethan Merritt :
On Wednesday 22 April 2009 09:23:19 Jacob Keller wrote:
Hello All,
What is the reason that x-ray fluorescence is neglected in our experiments?
Obviously it is measureable, as in EXAFS experiments to determine
anomalous edges,
but should it not play a role in the int
Because the fluorescence comes off in all directions, it makes a
significant contribution to the noise as one approaches the
resolution limit of the crystals, limiting the maximum resolution
attainable. So it would be a good idea to try to reduce it, e.g.
by choosing a suitable wavelength. Air
On Wednesday 22 April 2009 09:23:19 Jacob Keller wrote:
> Hello All,
>
> What is the reason that x-ray fluorescence is neglected in our experiments?
> Obviously it is measureable, as in EXAFS experiments to determine anomalous
> edges,
> but should it not play a role in the intensities as well?
Dear Jacob,
I think it is because the fluorescence is incoherent, and hence
contributes to the background rather than to the diffraction.
Congratulations, by the way, for managing to spell "fluorescence"
correctly twice within a short space! Usually it occurs as "flourescence",
which if
Hello All,
What is the reason that x-ray fluorescence is neglected in our experiments?
Obviously it is measureable, as in EXAFS experiments to determine anomalous
edges, but should it not play a role in the intensities as well? What am I
missing?
Jacob
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