FAQ5: How does one fit a doublet with a fixed area ratio, e.g. Cr 2p3/2
and Cr 2p1/2?

Peaks with known relationships, either spin-orbit or stoichiometric, can be modeled using constraints applied to the peak parameters. Figure 1 shows a Cr 2p doublet, where the two peaks are governed by a 2:1 ratio. An area constraint of this nature is introduced by relating a parameter in one synthetic peak to the corresponding parameter in another peak using the alphabetical label on the Components property page shown in Figure 2. The area in column B is constrained to be half that of the area in column A by entering the string A * 0.5 into the area constraint of column B. The FWHM and position for related peaks can be constrained is a similar fashion (see Figure 2).

Figure 1: Cr 2p Doublet.

Notes:

• The line-shapes are constructed from a linear combination of Lorentzian and Gaussian profiles where the asymmetric adjustments to the SGL profile are defined using the PHI tail function PHI(scale,length).
• Constraining two peaks in this way is not just physically superior but helps to reduce computation time during optimization.
• The Component annotation table shown in Figure 1 includes the constraints as part of the quantification table. This is optional and can be removed from the table if desired.

Figure 2: A sections of Components Property Page showing the columns with constraints used to construct a rigid peak model for a Cr 2p doublet.