Alan, I'm quite sure that Shay's pattern shows the typical profile for
a profile standard or any "highly crystalline" material measured with
a standard configuration of his instrument. No problem with sample
prep, no chance for improvement by modified instrumental setting
(thicker filter would reduce K beta but make the Ni absorbtion edge
more prominent). Unfortunately, lab instruments with "fast" 1D
detectors with high intensity efficiency but bad energy resolution
demanding for K beta filtering seem to be now the "quasi standard" on
the market. Low noise patterns can be measured in short time, but the
distorted profiles are hard to fit by simple standard profiles in a
similar quality. From this point of view it makes sense to find a
working approach for fitting the data of such machines, too.
However, I got several measurements showing Co or Cu K beta remnants
from users despite the manufacturer has claimed that the good energy
resolution of their detector (no names here!) alone would remove K
beta "completely". Sometimes the customers were adviced by the company
cases to insert an additional filter, and the "edge problem" is back...
Btw, I learned that even traditional secondary-beam curved graphite
002 monochromators are not always able to resolve a completely "clean"
Cu K alpha1/2 doublet: As the W L alpha wavelength is close to Cu K
alpha, in unfortunate cases (crystal quality or alignment) even such
machines may produce measurable/visible W L satellites when old tubes
are in use. For economic reasons, some people prefer to add a scalable
W L satellite peak in the BGMN wavelength model instead of buying a
new tube...
Personally, I love my Peltier cooled 0D Si drift detectors. They
really can completely suppress K beta and even remove any W L from Cu
K alpha, no need for scalable satellite peaks in the profile model.
Just some minor "wavelength feets" must be added to approximate the
ROI window. Practically, the profiles are comparable with the ones
obtained by a classical well aligned graphite monochromator plus
szintillation counter, but with 5 times more intensity. And the
detector may be used for some qualitative XRF (of course elements from
K- only, as in air).
Reinhard
Zitat von Alan W Hewat <alan.he...@neutronoptics.com>:
Reinhard is right that it is best to improve the instrument to produce
cleaner data. I'm concerned about the advice to model all kinds of features
whose origin is not fully understood, simply to obtain a better fit. Shay
has told us nothing about his instrument or his conditions of data
collection. He asks "Is it a sample preparation problem", to which
the obvious reply is "Do you see this with other samples or different
materials" ? Only he can answer that. If the answer is yes, he might try
modifying his instrument (remove filters etc) to see what effect that has
on the pattern from a simple well characterised material. Again only he can
do that. Data collection is an experimental science, and data refinement
should not be reduced to a "black box" computer program where extra
parameters can be added to reduce the R-factor.
Alan.
On Mon, 4 Sept 2023 at 08:18, Reinhard Kleeberg <
kleeb...@mineral.tu-freiberg.de> wrote:
Can be modeled in the BGMN peak profile model as well, by modifying
the *.lam file by a series of additional Lorentzians on the 1/lambda
scale, see figure.
The same can be done for other spectral impurities, e.g. W L
satellites. Also "electronic effects" on the wavelength distribution
profile like the "edges" from the ROI settings of Si drift detectors
can be modelled in such a convolution based approach.
However, better to have a pure/simple wavelength distribution (clear
alpha1/2 doublet) by a monochromator or high energy resolution
detector, as any satellites make trouble in trace phase analysis and
do cause prolonged calculation time in complicated Rietveld refinements.
Reinhard
Zitat von Matthew Rowles <rowle...@gmail.com>:
> Topas can model them quite well. The functionality was introduced in
> version 5.
>
> On Mon, 4 Sep 2023, 00:54 Kurt Leinenweber, <ku...@asu.edu> wrote:
>
>> Hi, Are these things modeled in Rietveld programs, by chance? It seems
>> like a lot of baggage to put in a refinement but if it makes the results
>> better…
>>
>>
>>
>> - Kurt
>>
>>
>>
>> *From:* rietveld_l-requ...@ill.fr <rietveld_l-requ...@ill.fr> *On
Behalf
>> Of *Thomas Gegan
>> *Sent:* Sunday, September 3, 2023 9:16 AM
>> *To:* Bish, David L <b...@indiana.edu>; Shay Tirosh <stiro...@gmail.com
>;
>> Fernando Igoa <fer.igoa.1...@gmail.com>
>> *Cc:* Rietveld List (rietveld_l@ill.fr) <rietveld_l@ill.fr>
>> *Subject:* RE: [EXT] Re: [External] Re: Step-like basline
>>
>>
>>
>> I agree with a Ni absorption edge, possibly with a Kβ peak around 38°
2θ.
>>
>>
>>
>> *Tom Gegan*
>> Chemist III
>>
>>
>>
>> Phone: +1 732 205-5111, Email: tom.ge...@basf.com
>> Postal Address: BASF Corporation, , 25 Middlesex Essex Turnpike, 08830
>> Iselin, United States
>>
>>
>>
>> *From:* rietveld_l-requ...@ill.fr <rietveld_l-requ...@ill.fr> *On
Behalf
>> Of *Bish, David L
>> *Sent:* Sunday, September 3, 2023 7:08 AM
>> *To:* Shay Tirosh <stiro...@gmail.com>; Fernando Igoa <
>> fer.igoa.1...@gmail.com>
>> *Cc:* Rietveld List (rietveld_l@ill.fr) <rietveld_l@ill.fr>
>> *Subject:* [EXT] Re: [External] Re: Step-like basline
>>
>>
>>
>> Some people who received this message don't often get email from
>> b...@indiana.edu. Learn why this is important
>> <
https://urldefense.com/v3/__https:/aka.ms/LearnAboutSenderIdentification__;!!IKRxdwAv5BmarQ!fFhSHn4S5iEzkW-O9lvWG-OzoqK_2SKhRniGa71nxuOL3GcxiyD83i2mnNN0Z48HPkn4zjKqH-aqqA$
>
>>
>> Hello Shay,
>>
>> I think it is probably related to "tube tails". You can read about this
in
>> the literature (e.g., on the BGMN web site) and you can model it in some
>> Rietveld software such as Topas. You don't normally notice this but it
>> becomes apparent with higher-intensity peaks.
>>
>>
>>
>> Regards,
>>
>> Dave
>> ------------------------------
>>
>> *From:* rietveld_l-requ...@ill.fr <rietveld_l-requ...@ill.fr> on behalf
>> of Fernando Igoa <fer.igoa.1...@gmail.com>
>> *Sent:* Sunday, September 3, 2023 3:06 AM
>> *To:* Shay Tirosh <stiro...@gmail.com>
>> *Cc:* Rietveld List (rietveld_l@ill.fr) <rietveld_l@ill.fr>
>> *Subject:* [External] Re: Step-like basline
>>
>>
>>
>> This message was sent from a non-IU address. Please exercise caution
when
>> clicking links or opening attachments from external sources.
>>
>>
>>
>> Hey Shay,
>>
>>
>>
>> Are you using a motorized slit during the measurement? These may open up
>> abruptly to compensate for the angular dependence of the footprint and
thus
>> generate an abrupt increase in the intensity.
>>
>>
>>
>> Hope it helps :)
>>
>>
>>
>> On Sun, Sep 3, 2023, 8:50 AM Shay Tirosh <stiro...@gmail.com> wrote:
>>
>> Dear Rietvelders
>>
>> I am attaching a zoom-in on a diffraction profile.
>>
>> My question is what is the origin of the step-like profile next to a
very
>> large reflection peak?
>>
>> Is it a sample preparation problem?
>>
>> Is it part of the baseline?
>>
>> Thanks
>>
>> Shay
>>
>> --
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
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--
TU Bergakademie Freiberg
Dr. R. Kleeberg
Mineralogisches Labor
Brennhausgasse 14
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Tel. ++49 (0) 3731-39-3244
Fax. ++49 (0) 3731-39-3129
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______________________________________________
Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE
<alan.he...@neutronoptics.com> +33.476.98.41.68
http://www.NeutronOptics.com/hewat
<http://www.neutronoptics.com/hewat>
______________________________________________
--
TU Bergakademie Freiberg
Dr. R. Kleeberg
Mineralogisches Labor
Brennhausgasse 14
D-09596 Freiberg
Tel. ++49 (0) 3731-39-3244
Fax. ++49 (0) 3731-39-3129
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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