But the edges for I and Hg are pretty far from CuKa (see attached). I
am familiar with their being extra signal (white lines) very close to
the peak, but not so far away....

JPK



On Wed, Jun 6, 2012 at 2:15 PM, Bernhard Rupp (Hofkristallrat a.D.)
<[log in to unmask]> wrote:
> There is also a relevant point from the physics of the absorption spectra -
> the XANES white lines (near edge peaks higher than the continuum transition
> or edge step) depend on the chemical environment of the anomalous atom in
> terms of available unoccupied states (which n. b. is something entirely
> different that the local neighbor environment/geometry which can be
> backtransformed - although with quite some uncertainty - from the EXAFS
> wiggles).
>
> Any argument about absolute f" peak values in absence of experimental
> evidence (scan) might want to consider that.....
>
> Best, BR

>
> -----Original Message-----
> From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of Jacob
> Keller
> Sent: Wednesday, June 06, 2012 11:30 AM
> To: [log in to unmask]
> Subject: Re: [ccp4bb] Fun Question - Is multiple isomorphous replacement an
> obsolete technique?
>

> No offense taken (we all have our dour moments!), but grant me a sincere
> question: the f" occupancy value would have been just as close at 11 as 5 if
> the true value were 8, am I correct? In other words, do you imply by saying
> "doing well" that you got as *much* as 5, or that you got as *close* as 5? I
> am just trying to see whether I understand these things correctly.
>
> Jacob
>
>
>
> On Wed, Jun 6, 2012 at 12:21 PM, Gerard Bricogne <[log in to unmask]>
> wrote:
>> Dear Jacob and all,
>>
>>     I realise that my last statement sounds awfully dour and
>> dismissive, in a way I really didn't intend. Especially as Stefan's
>> original posting was a "Fun Question".
>>
>>     Apologies to all for this over-the-top statement. I enjoyed a lot
>> of the replies.
>>
>>
>>     With best wishes,
>>
>>          Gerard.
>>
>> --
>> On Wed, Jun 06, 2012 at 06:09:33PM +0100, Gerard Bricogne wrote:
>>> Dear Jacob,
>>>
>>>      I thought that getting 5 for each iodine was doing pretty well,
>>> given the circumstances - e.g. the noisy measurements, the primitive
>>> software running on slow computers with tiny amounts of memory, etc. .
>>>
>>>      In any case my main point, directed at the original poster, was
>>> that reading the early Acta Cryst. issues ("RTFL") might be an
>>> alternative and perhaps more enlightening way of getting a picture of
>>> the evolution of phasing methods than finding some clever filter settings
> in the RCSB ;-) .
>>>
>>>
>>>      With best wishes,
>>>
>>>           Gerard.
>>>
>>> --
>>> On Wed, Jun 06, 2012 at 11:08:37AM -0500, Jacob Keller wrote:
>>> > ...Even with such primitive techniques, I can remember an HgI4
>>> > > derivative in which you could safely refine the "anomalous
> occupancies"
>>> > > (i.e. f" values) for the iodine atoms of the beautiful planar
>>> > > HgI3 anion to
>>> > > 5 electrons.
>>> >
>>> > I am surprised--f"'s of I and Hg are supposed to be around 8 for
>>> > CuKa (or maybe you weren't using CuKa)?
>>> >
>>> > JPK
>>> >
>>> >
>>> > --
>>> > *******************************************
>>> > Jacob Pearson Keller
>>> > Northwestern University
>>> > Medical Scientist Training Program
>>> > email: [log in to unmask]
>>> > *******************************************
>>
>> --
>>
>>     ===============================================================
>>     *                                                             *
>>     * Gerard Bricogne                     [log in to unmask]  *
>>     *                                                             *
>>     * Global Phasing Ltd.                                         *
>>     * Sheraton House, Castle Park         Tel: +44-(0)1223-353033 *
>>     * Cambridge CB3 0AX, UK               Fax: +44-(0)1223-366889 *
>>     *                                                             *
>>     ===============================================================
>
>
>
> --
> *******************************************
> Jacob Pearson Keller
> Northwestern University
> Medical Scientist Training Program
> email: [log in to unmask]
> *******************************************
>



--
*******************************************
Jacob Pearson Keller
Northwestern University
Medical Scientist Training Program
email: [log in to unmask]
*******************************************