To get back to Dirk's original question for Al and Si, I believe these satellites at low energy (relative to Ka emission) are due to the radiative Auger process (KLL RA in this case). Few X-ray catalogues report any satellites other that the typical ones that are from multiple ionizations and their effect on the Ka emission and are at higher energy than the Ka line. These light element spectra have low fluorescence yields, so much of the relaxation ends up being through electron emission, radiative and non-radiative Auger. Part of the radiative Auger process involves emission of an X-ray at or near the Auger electron energy. There is a peak in the Auger spectrum (measured by electron spectroscopy), and the radiative Auger spectrum (as measured by X-ray spectroscopy) for Si that is just above 1600eV, so at just above 30000 sin theta on TAP. Although this line is very subtle, expected to be at or below 0.01% of the Ka1,2 line, you can easily see it, particularly with a large crystal. When I measure the intensity on our LTAP, it is about 0.005% of the Ka emission. Note that this is a useful and interesting thing! Jun Kawai, I think, introduced the term EXEFS for this... Extended X-ray Emission Fine Structure. There are potential uses as details of this emission will be effected by band structure/bonding environment considerations.
The
K-L2,3L2,3 radiative Auger transitions correspond in energy (within a few eV) to the non-radiative Auger transitions.
The major Auger transitions are tabulated at
https://srdata.nist.gov/xps/A more comprehensive catalog of Auger transitions is given by:
Coghlan, W.A. & Clausing, R.E. (1973). Auger catalog calculated transition energies listed by energy and element.
Atomic Data 5, 317-469.
Examples of Mg K-LL RAE lines are in the attached file MgO-TAP-JEOL.pdf
Three TAP-crystal spectrometers were used on a JEOL8900R electron microprobe to scan the range 0.96 to 1.2 keV.
Both the
K-L2,3L2,3 and
K-L1L2,3 radiative Auger transitions of Mg are observed.
However, the same experiment using our Cameca SX100 gives an important difference!Spectra obtained with 3 TAP-crystal spectrometers on our Cameca X100 over the range 0.96 to 1.2 keV are in the attached file:
MgO-TAP-Cameca.pdf
Both the
K-L2,3L2,3 and
K-L1L2,3 radiative Auger transitions of Mg are observed.
Questions:
- What is the broad asymmetric peak at ~1.025 keV?
- Why does this peak have very different intensities on the 3 TAP-crystal spectrometers of the Cameca SX100?
This peak at ~1.025 keV is not a diagram line, not a satellite line, not a RAE line, and not a higher-order diffraction line.
It does not appear to be a multiple diffraction line (Renninger effect).
It is observable on Zn, Mg, Al, Si, and Zr elemental reference materials.
In these materials, it occurs at a fixed fraction of the energy of the principal diagram line of each element.
I would be very interested to know if others have observed this with TAP-crystal spectrometers.
Thanks, Andrew