X-ray Photoelectron Spin-orbit Splitting

In summary, the conversation discusses the process of fitting XPS spectrums using XPSpeak software. It is mentioned that for spin-orbit splitting, the FWHM and peak area ratios must be equal and the peak separation should be relatively constant. The question is raised about the variation of FWHM from different literature sources and the impact on fitting. The speaker shares their experience of getting a poor fit when using FWHM values from a website, but a good fit when only specifying FWHM invariance for each doublet. It is noted that the FWHM can be influenced by both intrinsic factors and instrumental resolution. The speaker also mentions that different oxidation states of Mo may have different FWHM values, but stresses
  • #1
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I have some XPS spectrums that I am trying to fit (my first time doing so), using XPSpeak.

I understand that for spin-orbit splitting the FWHM, line shape (i.e.% gaussian/lorentzian) must be equal (more or less), peak area ratios set (i.e. 2:3 for 3d3/2 and 3d5/2), and the peak separation (relatively) constant.

My question is, how much can the FWHM vary from different literature sources?

The area I am fitting is the Mo 3d area, if I contrain the FWHM to the values I found at www.xpsfitting.com I get a pretty poor fit. However, if I only constrain the peak FWHM's to be equal (for each doublet), and not explicitly specifiy; I get a good fit.

For example, one doublet is the MoO3 3d. The FWHM (Mo 3d3/2) specified at the website I previously mentioned is about 0.86. If I only specify that the doublet must have FWHM invariance (and not explicitly 0.86) the FWHM becomes 2.82 after optimization.
 
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  • #2
There are at least two contributions to the FWHM: The intrinsic width of the peak given by the life time (lorentzian) and whatever may influence the peak position (impurities, strain, ..., probably gaussian), and the instrumental resolution (most likely gaussian).

If you measure the same sample on two different instruments with different resolution you will find two different widths.

Try to check your reference literature for specifications of the instrumental resolution.

0.86 sounds more reasonable for intrinsic width than 2.82, so your instrument may have a fairly broad resolution. Are the settings fully optimized?
 
  • #3
I am working with Mo oxides and trying to fit XPS measurements also. I understand that for doublets, the FWHM value should be the same, and different for each instrument and sample. However, should be the FWHM value the same for the different Mo oxidation states (Mo4+, M05+ and Mo6+) in the same measurement?
 

1. What is X-ray Photoelectron Spin-orbit Splitting?

X-ray Photoelectron Spin-orbit Splitting is a phenomenon observed in X-ray photoelectron spectroscopy, where the energy levels of electrons in a sample are split due to the interaction between their spin and orbital angular momentum.

2. How does X-ray Photoelectron Spin-orbit Splitting occur?

X-ray Photoelectron Spin-orbit Splitting occurs when a sample is exposed to X-rays, causing electrons in the sample to be excited and ejected. The ejected electrons then experience a splitting of their energy levels due to the interaction between their spin and orbital angular momentum.

3. What is the significance of X-ray Photoelectron Spin-orbit Splitting?

X-ray Photoelectron Spin-orbit Splitting is significant because it provides valuable information about the electronic structure of a sample. The energy levels and splitting patterns can reveal details about the types of atoms present and their bonding within the sample.

4. How is X-ray Photoelectron Spin-orbit Splitting measured?

X-ray Photoelectron Spin-orbit Splitting is measured using X-ray photoelectron spectroscopy, which involves bombarding a sample with X-rays and measuring the kinetic energy of the ejected electrons. The resulting energy spectra can then be analyzed to determine the spin-orbit splitting.

5. What are some applications of X-ray Photoelectron Spin-orbit Splitting?

X-ray Photoelectron Spin-orbit Splitting has many applications in materials science, chemistry, and physics. It is commonly used to study the electronic properties of surfaces, thin films, and interfaces. It can also be used to identify and characterize different elements in a sample and to study their chemical states.

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