silly question time - emission profiles

matsmcfly1

Hi everyone,

I have a silly question, the answer to which I should really know...

I am setting up some input files for our different instruments and I have realised that I dont know what the lh parameter is when creating the emission profile. In the technical notes I can find a table of the default values, but not what it (physically) is - can anyone clear this up for me?

Also, we have an instrument that provides Ka1, Ka1 and Kb - how do I incorporate the Kbeta in the emission profile? I can add another line, but I dont know what the la value should be for this:

lam
	ymin_on_ymax  0.0001
	la  0.5           lo  1.54060      lh  3.6854               '' Ka1
	la  0.5           lo  1.54439      lh  0.437                 '' Ka2
	la  @ 0.05     lo  1.39222      lh  @ 0.01              '' Kbeta

However, if I remember back a few years I seem to recall that is we are using a nickel foil to filter out the Kbeta that we should include an absorption edge correction - does anyone have an example of using this in their input file?

Any advice or questions will be welcome 🙂 Thanks!

matsmcfly1

I might have just answered my own question here whilst trawling the wiki:
"la: Area under the emission profile line
lo: Wavelength in [Å] of the emission profile line
lh: HW in mÅ of a Lorentzian convoluted into the emission profile line.
lg: HW in mÅ of a Gaussian convoluted into the emission profile line."

So in short, la = the relative contribution from the wavelength lo, and lg or lh is an emission profile shape parameter that is obtained from refinement of the instrment model (and should be fixed for sample refinement) - is this correct?

djurdjijadzodan

Dear colleague(s),

Thank you for your question, I have been wondering the same.

If I know that the "CuKalfa5Berger" emission profile describes in the best way the emission profile of the diffractometer (with the Ni filter installed as well) that I have used to collect the XRDs (as far as I am seeing no K beta component of the radiation is listed in the JEdit script upon selecting the "CuKalfaBerger" emission profile) and if I also know that the X-ray tube is relatively "old" (based on that fact I have understood that the absorption edge correction should be applied as well) does it also mean that I will need to find a way to include the Kbeta component of the radiation among the following code lines that represent the emission profile, and if yes how exactly:

 lam                                                   
	ymin_on_ymax  0.0001
	la  0.0159 lo  1.534753 lh  3.6854
	la  0.5691 lo  1.540596 lh  0.437
	la  0.0762 lo  1.541058 lh  0.6
	la  0.2517 lo  1.54441 lh  0.52
	la  0.0871 lo  1.544721 lh  0.62

I haven't managed to figure out your last conclusion.

Looking forward to hearing from you soon.

Kind regards,
Djurdjija

rowlesmr

Yes, lh and lg are the lorenztian and gaussian fwhm of the indiviudal peaks that have been fitted to the experimental Cu (and other anodes) emission profiles.

Yes, you will see kB peaks with a metal filter. What I do is something like:

   lam ymin_on_ymax 0.0001 
   prm kB_scale 0.05 min 0.0001 max 0.5
   Lam_recs
   {
      0.378  1.7889847	0.4633522  
      0.144  1.7892524	0.6958819 
      0.127  1.7896946	1.1767380 
      0.088  1.7888515	0.2085420 
      0.197  1.7927905	0.6237179 
      0.095  1.7930637	0.7190761 
      0.050  1.7934738	1.1578452 

	=kB_scale 0.449;	 1.6207938	0.6462327
	=kB_scale 0.189;	 1.6211689	0.7588800
	=kB_scale 0.153;	 1.6228580	2.0774644
	=kB_scale 0.103;	 1.6216651	1.0372054
	=kB_scale 0.082;	 1.6236359	2.8895524
	=kB_scale 0.025;	 1.6198346	0.8020733
   }

That incorporates the ka and kB emission profiles, with a refineable scalefactor for the betas. I normally fix that after refining on a nicely crystalline standard.

matsmcfly1

rowlesmr thanks muchly for this, I will give this a try for my data 👍