[Ifeffit] [Ext] Dumb question

[Robert Gordon]

OK...my first impulse would be to plot the full unnormalised XANES on the
same graph so you can see the features grow in or change.
If there are a large number of scans, maybe only plot every 3rd or 4th or
such. You might find a better point to examine for time dependence
than the one you had used.

Sorry...I'm not clear on the type of experiment. Is it something where the
concentration should be increasing, like dissolving in solution,
or a chemical change - concentration of target element is constant, but
chemical form changes, so features in the XANES are changing
or shifting.

In the datafile, are there column headings? Do any of them indicate a dead
time corrected value?
You may need to ask the person who collected the data or the beamline if
such a correction is warranted.

More generally, how much background in X-ray work do you have? Have you had
a course on it?
Do you know how dead time arises for a solid state detector?

If you are looking at the increasing concentration scenario, as the signal
rises, the detector has to reset before counting more.
The higher the signal, the more time spent resetting instead of counting -
the time over which the detector is live is less than
the real time over which you are integrating. A strong white line feature
could be a bad choice for
monitoring over time in this regard without the correction. Look at other
features. Is there a pre-edge feature you could use?
Even the pre-edge background could be indicative of concentration
saturation.

If it is the chemical change scenario, then just look for when it stops
changing.

Sorry if this is vague. Hope it helps.

-R.




On Fri, Feb 17, 2023 at 11:16 AM Roberta Candela <rjcandel at asu.edu> wrote:

> Yes I think that would be the plot. I currently haven’t been normalizing
> anything as I was just trying to see if I could get a rough draft. I
> haven’t done any background removal it was essentially just the raw data.
> As far as the features go I am not sure? I wasn’t trying to target a
> specific feature. The fluorescence was measured using a solid state
> detector but I’m not sure about the dead time. Is that information that is
> contained in xdi files? I wasn’t at this particular beam time so I have
> only the file to work off of.
> Thank you so much for the detailed response!
> -B
>
>
> Sent from Yahoo Mail for iPhone
> <https://overview.mail.yahoo.com/?.src=iOS>
>
> On Thursday, February 16, 2023, 2:50 PM, Robert Gordon <
> ragordon at alumni.sfu.ca> wrote:
>
> So your goal is to plot If/I0 versus time for a given energy in the XANES.
> Are you exporting normalised XANES or just If/I0?
> Are you doing background removal from the pre-edge?
>
> Is another feature underlying this targeted feature also disappearing or
> changing? i.e. you are not watching a feature
> increase from zero but instead changing from one to another? ...or seeing
> a background increase as well?
>
> Was the fluorescence measured using a solid state detector? Did the
> deadtime of the detector increase significantly
> as the signal from the sample increased (and no deadtime correction
> applied) ?
>
> -R.
>
>
>
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