Simulation of V Complex

[Koffe]

Dear all,

I am a beginner and struggling to simulate this spectrum. This spectrum is the ESR spectrum of vanadium compounds in powdered form at room temperature. My goal is to calculate accurate g-values and A-values through fitting.

Although I used the following code for fitting, the results were not satisfactory. As you can see from the shape of the residuals, there is significant broadening in the spectrum.

From my literature research, I found that such broadening is often explained as being caused by superexchange interactions of electrons along V(IV)-O-V(V) bonds. I believe this could be the case here as well.

I would greatly appreciate any guidance, opinions, or specific suggestions for improving the code.

Best regards,

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Sys1.g = [1.973, 1.933];
Sys1.A=[192.8 523.7];
Sys1.Nucs = '51V';
Sys1.lwpp = 1.5;
Sys = {Sys1};

Exp.mwFreq = 9.2;
Exp.Range = [169.105 469.105];
Exp.nPoints = 65536;

Vary1.g = [0.05, 0.05];
Vary1.A = [20 20];
Vary1.lwpp = 1.0;
Vary = {Vary1};

esfit(spc,@pepper,{Sys,Exp},{Vary});
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ESR spectrum.png (140.22 KiB) Viewed 11238 times

[Stefan Stoll]

If you have superexchange coupling between two V, then you have to define a spin system with two electron spins and two 51V nuclei. You'll need Sys.S = [1/2 1/2] and Sys.Nucs =51V,51Vand a value inSys.J.Sys.AandSys.g` must contain all A and g tensors. See the documentation on spin systems on how to define these for multi-spin systems.

[katarkon]

It is clear superposition of at least two signals. You try to simulate only one of them.
Another signal should have sufficiently larger linewidth and relative weight. If it occur due to superexchange V-V coupling, it is almost unreliable to extract its parameters correctly, except special cases J<<A either J>>A.