Hello,

In XPS measurements, I am observing consistent shifts in spin-orbit splitting values for different oxides of the same base element. I'm being told by many that this is not possible, that the spin-orbit split is an intrinsic property, and is therefore an error with my data collection method or data fitting. I'm fairly confident in my peak positions, but less confident in charge neutralization (since I didn't collect all of this data myself I don't have a solid record). Regardless, I would assume that components of the same spectra (i.e. 2p(1/2) & 2p(3/2)) should shift linearly for a charged surface. As a side note, all pass energies and collection step sizes have been the same throughout these measurements.

Is it possible to have different spin-orbit splitting values for various compounds or stochiometric variations of a compound containing the same element? (For example A0 v. AX2 v. A2X3 )

One of my thoughts is that magnetic domains might have a localized Zeeman effect on spin-orbit split components. Some folks I work with have done XPS measurements on superconductors before and after Tc , and they didn't observe a shift in spin-orbit split values. That being said, they aren't convinced what we are seeing could be related to ordering or magnetism. It just makes sense to me that spin-orbit split components can be shifted just by their crystallography or magnetic structure, by how much I just don't know. The shifts I see range from 0.2 - 0.5 eV between compounds.

Would anyone agree with this guess, if not, could you provide a physical justification for what I'm seeing? I'm fine with any suggestions on the instrument setup or physicality of a materials system.

Thank you.

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