Armel,
why do you like playing with numbers so much ? Well, I can tell you some
more :
suppose you can subdivide your (our) interval (0-180 degs 2theta) into
small parts, say 0.01 degs. In other words, you may have 180000 channels
at maximum. If there is an "useful" intensity in a channel (not only a
background, i.e.) you can attribute that channel "1", "O" otherwise. Than
you have less than 180kB of information at maximum. What can you do with
such a information rubbish ?
Best,
Lubo
On Sat, 25 Sep 1999, Armel Le Bail wrote:
> >I converted the data to 2th, using a popular synchrotron
> >wavelength (0.7 A) for everybody's convenience. You can see by yourself
> >that the 200 peak has about 0.013 degrees FWHM. Clearly, the FWHM depends
> >on the wavelength you choose, so I guess I could have gotten to 0.006 using
> >a shorter wavelength. As I already said, what matters is the deltad/d
> >resolution, in this case 7x10-4.
>
> Of course, it matters also for poor conventional X-ray powder
> diffractionists which have generally only one wavelength at their
> disposal (1.54A). But due to this fact, they (at least me) have this
> reference in mind : FWHM= 0.04� (2th) at 1.54A. So that, when
> synchrotron data claim FWHM = 0.02� at 0.77A, we (at least I)
> just think that, well, this is the same that we can do at home ;-).
> We can also transform our 1.54A data into 0.77A data and divide
> the FWHM by almost a factor 2. But this is not the game we want
> to play here.
>
> This was the subject of poster P07.01.001 at IUCr XVIII, Glasgow .
> The whole poster may be seen at :
> http://sdpd.univ-lemans.fr/glasgow/poster/glasgowposter.html
>
> As a conclusion, in "equivalent conventional X-ray at 1.54A", your
> MgO pattern presents FWHM ~0.03�, when I was expecting 0.006�.
> But it is really fine, for neutron data, and it is better than we can
> do (unless enlarging our diffraction radius, like on synchrotron
> instruments, but with large intensity lost).
>
> Best,
>
> Armel
>
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