I got from here http://webhome.phy.duke.edu/~kolena/hou/counts.html a formula for the number of counts (c=faqt; where c is the number of counts, f is the photon flux, a is the area, q is the quantum efficiency and t is the exposure time) It is for telescopes but I guess is not a lot different for the detector used in xrc.

Thank you very much.



El mié., 6 de mar. de 2019 a la(s) 19:20, Johan Hattne (hattne@ucla.edu) escribió:
I think that would depend on how the detector is measuring the photons that impinge on it.

Unless you’re actually concerned with exactly how the detector does its thing, I think Tim’s dimensionless or something fuzzy like “detector unit” is fine.

// Johan

> On Mar 6, 2019, at 14:16, Murpholino Peligro <murpholinox@gmail.com> wrote:
>
> ...
> The counts are the number of x-ray photons converted to electrons?
>
>
> Thanks
>
> El mié., 6 de mar. de 2019 a la(s) 15:18, Tim Gruene (tim.gruene@psi.ch) escribió:
> Dear Murpholino,
>
> the unit of intensity is '1' - it is the counts on the detector. The scale is
> arbitrary, you can multiply your intensity with any positive number you want,
> as long as you don't create an overflow or underflow in the computer program.
>  As long as you do the same with the sigma-values, your refinement should not
> change.
>
> Best regards,
> Tim
>
> On Wednesday, March 6, 2019 10:00:55 PM CET Murpholino Peligro wrote:
> > If I do `phenix.xtriage XDS_ASCII.HKL` I get a log file. In the "Statistics
> > for data merging" of this log file I have:
> >     Resolution: 26.02 - 1.40
> >     Observations: 44675
> >     Unique reflections: 16306
> >     Redundancy: 2.7
> >     Completeness: 70.37%
> >     Mean intensity: 1656.8
> >     Mean I/sigma(I): 19.8
> >     SigI < 0 (rejected): 644 observations
> >     R-merge: 0.027
> >     R-meas:  0.032
> >     R-pim:   0.017
> >
> > My question is... what units does Mean intensity has?
> >
> > Thanks
> > Ps I am not sure if this has to do with the detector used which was a CCD
> > (type) ADSC QUANTUM 210 (model).
>
> --
> --
> Tim Gruene
> Head of the Centre for X-ray Structure Analysis
> Faculty of Chemistry
> University of Vienna
>
> Phone: +43-1-4277-70202
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