Summary: How to explain phase determinaton and Fourier

Nobuhisa Watanabe nobuhisa at kekvax.kek.jp
Sat Sep 17 23:31:22 EST 1994


I have received ten responses by e-mail for my post. And the half of them 
are asking to post the summaries here. 

The answer for the question: "How can you get an electron density maps 
from the diffraction spots?" is,

1) Diffraction.
Almost all wrote the only one way to explain the diffraction is using He-Ne

laser with some meshes, slits, or photo reduced two dimensional patterns.

2) Phasing.
I think there is no good idea to explain phasing to the "public".
"Using some tricks" is enough?

3) Fourier transform.
Using Prof. Henk Schenk's overhead projector method might be most
impressive.

>he had some sheets for the overhead projector with some parallel lines, 
>representing the waves.
>He put them ('quite randomly') on top of each other and the result was a
>rather featureless, blurred picture. Then he started to explain about 
>direct methods etc. and after that he put the sheets on top of each other 
>again (but this time properly aligned i.e. all corners on top of each other)
>and the electron density map of a benzene ring emerged ...

I know what it is. But I do not know there are any references. Please post 
here if someone knows any references. And I wonder if someone copy this to 
a nice software using graphics? 

#I found I made a mistake when I post the previous question. 
#I am very sorry for inconvenience.
-- 
Nobuhisa WATANABE
Photon Factory, Natinal Laboratory for High Energy Physics
e-mail: nobuhisa at kekvax.kek.jp




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