[Sasview-users] Extraction of form and structure factor

[Andrew Jackson]

Dear Marco

Richard is pointing to a new feature that should be in release 4.1 – it was added at the last Code Camp (in October), which was after the version 4 release.

The separated form and structure factors will then appear in the Data Explorer under the data set you have fitted, similarly to how the fitted curve and residuals appear now (see screen shot).

We are aiming to have the 4.1 release out in early 2017.

Best
Andrew

______________________________________

Andrew Jackson

Instrument Scientist - Small Angle Scattering
European Spallation Source, P.O Box 176, SE-221 00 Lund, Sweden



Adjunct Associate Professor (Adjungerad Lektor)
Physical Chemistry, Lund University, P.O. Box 124, SE-221 00, Lund, Sweden


Phone: +46 46 888 3015

Mobile: +46 72 179 2015

E-mail: a<mailto:andrew.jackson at ...631...>ndrew.jackson at ...631...


www.esss.se


From: Richard Heenan <richard.heenan at ...8...<mailto:richard.heenan at ...8...>>
Reply-To: Mailing list for users of SasView <sasview-users at ...632...e.net<mailto:sasview-users at lists.sourceforge.net>>
Date: Thursday 24 November 2016 at 13:44
To: "m.adamo15 at ...625...<mailto:m.adamo15 at ...625...>" <m.adamo15 at ...625...<mailto:m.adamo15 at ...625...>>, "users at ...2...<mailto:users at ...2...>" <users at ...2...<mailto:users at ...2...>>
Subject: Re: [Sasview-users] Extraction of form and structure factor

Dear Marco,

Yes alas version 3 of sasview does not make it easy to save the S(Q). I suspect here that you have not allowed for the fitted flat background, which you will need to subtract, or set to zero and recalculate, before doing the division.

In the new version 4 of sasview, the separate P(Q) and S(Q) are supposed to appear in the data structure on the left of the screen along with the total fit.   I only say “supposed” in that in some of our very recent builds some other changes made this new feature disappear, and without going to look I am not sure of the current status on the public downloads.

Hope this helps
Richard Heenan



From: Adamo, Marco [mailto:m.adamo15 at ...625...]
Sent: 24 November 2016 11:13
To: users at ...2...<mailto:users at ...2...>
Subject: [Sasview-users] Extraction of form and structure factor

Dear SasView team,

I have some corrected SANS data that I am fitting with SasView. The system is SDS 10% in 90% D2O/20% H2O v/v (file 093220_230).
I was able to fit it with "EllipsoidModel”,  “HayterMSAStructure” (file M2[093220_230_out.txt). Could you please explain me how to extract the structure and form factor?

What I tried was to:

1.       Fit the data with the above mentioned model

2.       Remove the structure factor (just by deselecting it in SasView) to obtain ONLY the form factor (no more fit was performed, only the calculation)

3.       Save the curve that is supposed to be a form factor

4.       Divide the original data by the form factor to get the structure factor

If I do the other way round, so I fit the data, remove the form, fix the structure factor (RED) and from it I get the form (PURPLE CIRCLES) by dividing the original data (BLUE)  by the structure, I get this curve:

[cid:image001.png at ...629...]

The problem is that I do not see any realistic form factor, as the structure is not completely removed at low q. Do you have any suggestions, please?

Thanks,
Marco
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.sasview.org/cgi-bin/mailman/private/users/attachments/20161124/1daae392/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.png
Type: image/png
Size: 19067 bytes
Desc: image001.png
URL: <http://lists.sasview.org/cgi-bin/mailman/private/users/attachments/20161124/1daae392/attachment-0002.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Screen Shot 2016-11-24 at 15.27.15.png
Type: image/png
Size: 84348 bytes
Desc: Screen Shot 2016-11-24 at 15.27.15.png
URL: <http://lists.sasview.org/cgi-bin/mailman/private/users/attachments/20161124/1daae392/attachment-0003.png>