[Sasview-users] Extraction of form and structure factor

[richard.heenan at ...8...]

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...
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
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