Questions about MAN background use

[John Donovan]

3 - Yes, I asked you about "interpolated off-peak  MAN" method. What equation the system apply to calculate "on peak" background for MAN curve - the equation we have chosen for "off peak" background correction?

The interpolated off-peak MAN method utilizes whatever off-peak (or MPB) fit method is assigned to that standard sample (from the Elements/Cations dialog).

[Rom]

Great!
John, thank you very much.

[Rom]

Greetings John and everyone!
Could you help to find a solution to compare background levels (for MAN curve) of the same standard/element which was measured at the same conditions but in different sessions (different MDB).
I tried to upload the standard measuring from different sessions with standard way (acquisition/new sample/... way) but it is impossible? because  the system will be confused?
I wonder to use a set of identical data to obtain an average for routine measurements of main elements.
Also we can quick (just quality) compare a contamination of minor elements in the close samples which were measured in different sessions etc.
Thank you a lot.
 

[Probeman]

Could you help to find a solution to compare background levels (for MAN curve) of the same standard/element which was measured at the same conditions but in different sessions (different MDB).

If you want to compare MAN background values from multiple runs you should be able to export those using the Output | Save User Specified Format Output menu from each run and compare them in an external program.  Note also from the Output | Save Custom Analysis Output menu there is a Format #8 (MAN) output menu that might also be useful.

I tried to upload the standard measuring from different sessions with standard way (acquisition/new sample/... way) but it is impossible? because  the system will be confused?

You can also import standards into Probe for EPMA from multiple MDB files using the Acquire! window, New Sample/Setup button dialog, Load File Setup button, but you'll need to (completely) close Probe for EPMA, before loading the same standards from other probe runs. Hey, it's a feature, not a bug!   

Then once you have all the multiple (MAN) standards loaded from all your runs, you can open the Analytical  Assign MAN Fits menu and then *uncheck* the Plot Last MAN Set Only checkbox as seen here:

[Anette von der Handt]

Or you could use "Drift.exe" and just search for a specific element or element/standard combination. It should tabulate all the intensities over all the mdbs with time stamps into a single xls spreadsheet. However, these intensities are not corrected for continuum absorption. Nevertheless, drift makes it easy to compare how the intensities vary from run to run over time.

[AndrewLocock]

S - Bi interference?!

I recently found a subtle(!) error in my methodology using MAN backgrounds:
the apparent interference of the S absorption edge on Bi M-alpha measured on PET.
I thought that this might be of interest to the community, and so am describing it here.

Using Bi2Te3 as the Bi-standard, and having established a precise MAN curve for Bi M-alpha, I thought all would be well.
However, the subsequent Bi contents of the various sulfide minerals were substantially above detection limits (unexpected, and almost certainly incorrect).
A clue: all the standard materials that contain sulfur fall well off the established MAN curve for Bi M-alpha.

However, no spectral interferences are listed by Probe-for-EPMA software for Bi M-alpha by sulfur.
What is going on?

I finally looked at the WDS scans of bismuth selenide, ZnS, and FeS2 tabulated by Sandrin Feig at Central Science Laboratory: EPMA - Method Development Tool.
The absorption edge for S is close to S K-beta, and this edge leads to a slightly elevated background under the Bi M-alpha position.
I think that, when large amounts of S are present, this elevation of the background leads to a misleading small value for analyzed Bi.

I suppose that I could move to the Bi M-beta line to avoid the problem.
But for the present, I simply put in an overlap correction, using synthetic ZnS (99.995% purity).

I would be interested in the experience and opinions of others on this apparent problem.
Thanks, Andrew

[Probeman]

Interesting. My general "rule of thumb" for background (off-peak or MAN) is that it's generally the lowest intensity one can measure.  Again, just a "rule of thumb", there are exceptions (holes in the continuum, e.g., Au La in Fe bearing minerals).

Can you share a screenshot of the plot for the Bi La MAN calibration curve with us?

[AndrewLocock]

Interesting. My general "rule of thumb" for background (off-peak or MAN) is that it's generally the lowest intensity one can measure.  Again, just a "rule of thumb", there are exceptions (holes in the continuum, e.g., Au La in Fe bearing minerals).

Can you share a screenshot of the plot for the Bi La MAN calibration curve with us?

Attached is a PDF of the Bi M-alpha MAN assignment and fit.
The 8 reference materials used in this fit are: Cr2O3 (#2), TiO2 (#5), MgAl2O4 (#13), Cr (#27), Ag (#34), Ti (#45), Sb (#55), and SiC (#133).
The relative-percent-deviation is 1.79, the intercept is -0.0135, and the Z-fraction is the default 0.7.

Also attached is a PDF of wavelength scans (JEOL units, PETJ) from Sandrin Feig's excellent EPMA-Method Development Tool.
The S K-edge should be circa 160.7 mm, and the scans shown include: Bi2Se3, ZnS, and FeS2.
There is a tail from S K-beta1 on its high side, which extends under the Bi M-alpha peak (at about 164.0 mm).
I attribute this tail to the effect of the S K absorption edge.

This S-related tail presumably gives rise to fictive Bi M-alpha intensity, when S is abundant.

[AndrewLocock]

I attribute this tail to the effect of the S K absorption edge.

Upon closer inspection, the tail on the high side of S K-beta cannot be due to the S absorption edge.
If anything, the effect of the S absorption edge would be to lower(!) the background in this region.
Attached is a plot of the S K-edge in JEOL units for a PET crystal.
And a plot of the Ar and S K-edges in a scan of marcasite from Sandrin Feig's EPMA-Method Development Tool.

So, what gives rise to the elevated background between the S K-beta and S K-alpha peaks?
Particularly, close to the S K-beta peak (on the high JEOL mm side, which is the low energy side)?

I will have to check where are the radiant-Auger emission lines for S.

[AndrewLocock]

I will have to check where are the radiant-Auger emission lines for S.

Bingo! (possibly).

From the Auger emission catalog of Coghlan & Clausing (Atomic Data 5, 317-469, 1973):
For sulfur, the KM1M1 Auger emission line is at 2.438 keV, and the KM1M23 Auger emission line is at 2.4475 keV.
It is possible for Auger transitions to be present in X-ray spectra as radiant-Auger-emission lines.

In the attached scans of Bi2Se3 and FeS2 from Sandrin Feig's EPMA Method-Development Tool, there are small peaks at 2.437 and 2.445 keV.
Bi M-alpha is at 2.422 keV in this image.

So, now my interpretation is that tails from S Auger-emission lines near S K-beta are interfering on the Bi M-alpha line.
If this is correct, it might be useful to have the various Auger-emission lines added to programs such as Probe-for-EPMA,
and the EPMA Method-Development Tool.

[Probeman]

Interesting. My general "rule of thumb" for background (off-peak or MAN) is that it's generally the lowest intensity one can measure.  Again, just a "rule of thumb", there are exceptions (holes in the continuum, e.g., Au La in Fe bearing minerals).

Can you share a screenshot of the plot for the Bi La MAN calibration curve with us?

Attached is a PDF of the Bi M-alpha MAN assignment and fit.
The 8 reference materials used in this fit are: Cr2O3 (#2), TiO2 (#5), MgAl2O4 (#13), Cr (#27), Ag (#34), Ti (#45), Sb (#55), and SiC (#133).
The relative-percent-deviation is 1.79, the intercept is -0.0135, and the Z-fraction is the default 0.7.

Also attached is a PDF of wavelength scans (JEOL units, PETJ) from Sandrin Feig's excellent EPMA-Method Development Tool.
The S K-edge should be circa 160.7 mm, and the scans shown include: Bi2Se3, ZnS, and FeS2.
There is a tail from S K-beta1 on its high side, which extends under the Bi M-alpha peak (at about 164.0 mm).
I attribute this tail to the effect of the S K absorption edge.

This S-related tail presumably gives rise to fictive Bi M-alpha intensity, when S is abundant.

When you first described this issue I thought it was because you might have been using some sulfur containing materials for your MAN curve for Bi Ma, but now I see that you did not. So this is actually just a normal spectral interference issue and is properly corrected just as you did by utilizing a standard containing sulfur, but no Bi.

Or am I missing something?

[AndrewLocock]

So this is actually just a normal spectral interference issue and is properly corrected just as you did by utilizing a standard containing sulfur, but no Bi.

No, unfortunately, this is not just a normal spectral interference issue.
It is interference by Radiative-Auger-Emission lines (RAE lines) on the Bi M-alpha X-ray emission line.

The closest interferences given by the Probe-for-EPMA software in the vicinity of the Bi M-alpha line are shown in the attached JPG file.
The only interference listed as coming from sulfur is the S SKBN line, about -1.645 mm away from the Bi M-alpha line.

Whereas there are 2 RAE lines of sulfur, S KM1M23 and S KM1M1 that are closer to the Bi M-alpha position.
Please see the attached PDF, which shows the S RAE lines with respect to the main emission lines and satellite lines of sulfur.

As the RAE lines are not always insignificant, my suggestion is that they be included into the Probe-for-EPMA software in some fashion.
The Coghlan & Clausing 1973 reference is a good start for lines between 10 eV and 3000 eV.

Some further examples of RAE lines in X-ray emission spectra are given by Takahashi et al. (2001) Extended x-ray emission fine structure and high-energy
satellite lines state measured by electron probe microanalysis. Surface and Interface Analysis 31, 118-125.

[John Donovan]

So this is actually just a normal spectral interference issue and is properly corrected just as you did by utilizing a standard containing sulfur, but no Bi.

No, unfortunately, this is not just a normal spectral interference issue.
It is interference by Radiative-Auger-Emission lines (RAE lines) on the Bi M-alpha X-ray emission line.

OK, that is cool.  But the Calculate WDS Interferences button in PFE is just a nominal calculation for trying to figure out these interferences in a general sense. This nominal calculation has nothing to do with the actual quantitative spectral interference correction in PFE.  So if the nominal calculation doesn't list a specific interference, that doesn't mean it can't be corrected for.

In other words if a material with S but no Bi shows a positive net intensity it could be a contamination, or an interference from another element, or an interference from the element in question.

If these Auger lines are actually detectable, it would be neat to include them as a calculation/display option. But the quantitative interference correction itself should take of care of it either way is my assumption.

Did you try the quantitative interference correction using a standard with S but no Bi?  How does it do?

[AndrewLocock]

So this is actually just a normal spectral interference issue and is properly corrected just as you did by utilizing a standard containing sulfur, but no Bi.

No, unfortunately, this is not just a normal spectral interference issue.
It is interference by Radiative-Auger-Emission lines (RAE lines) on the Bi M-alpha X-ray emission line.

OK, that is cool.  But the Calculate WDS Interferences button in PFE is just a nominal calculation for trying to figure out these interferences in a general sense. This nominal calculation has nothing to do with the actual quantitative spectral interference correction in PFE.  So if the nominal calculation doesn't list a specific interference, that doesn't mean it can't be corrected for.

Did you try the quantitative interference correction using a standard with S but no Bi?  How does it do?

The Probe-for-EPMA software is so useful and reliable, that I am guilty of relying on it to figure out my interferences for me!
That is, I am (or have been) highly reliant on PFE's "nominal calculation" to indicate all probable interferences.
This is why I suggest adding in the RAE lines (perhaps just those from 0.6 to 3.0 keV, observable on TAP and PET).

And yes, as I mentioned in my first post on this topic - I simply put in an overlap correction, using synthetic ZnS (99.995% purity).
It works sufficiently well, thank you!

[John Donovan]

Did you try the quantitative interference correction using a standard with S but no Bi?  How does it do?

The Probe-for-EPMA software is so useful and reliable, that I am guilty of relying on it to figure out my interferences for me!
That is, I am (or have been) highly reliant on PFE's "nominal calculation" to indicate all probable interferences.
This is why I suggest adding in the RAE lines (perhaps just those from 0.6 to 3.0 keV, observable on TAP and PET).

And yes, as I mentioned in my first post on this topic - I simply put in an overlap correction, using synthetic ZnS (99.995% purity).
It works sufficiently well, thank you!

Ok, great, just double checking.

If someone has a ASCII table with these Auger lines feel free to post it.  We would like to have at least the text labels, energies and nominal intensities for each emission line.