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Hi EPR experts,

I am trying to fit a Cu X band spectrum, but I can't seem to get the broadening correct in the Cu HF.

For what its worth, this sample is predominately aqueous Cu(II) with some acetate coordination, and there is a minor Cu(II) component with 2 N's bound (hence the weak N hyperfine signal in the g⟂). At the moment I am trying to fit the spectra using a single Cu component, as the N-bound Cu(II) species is very low in concentration and difficult to quantitate from the spectrum.

Below is the code used for the simulation, with values of g, A and gstrain which correspond to the best fit shown in the attached image.

Any tips on where I am going wrong with the broadening are much appreciated, thanks in advance.

-Macon

[B1,spc1] = textread('avg_all_1xOct3.txt','%f %f');

Exp.mwFreq = 9.1881; %GHz
Exp.Range = [min(B1) max(B1)]; %mT
Exp.nPoints = numel(B1);
Exp.ModAmp = 0.4; %mT
Exp.mwPhase = 0; %
Exp.Harmonic = 1;

Sys.g = [2.08779 2.05434 2.22563];
Sys.A = [62.8793 30.9288 567.909]; % MHz
Sys.Nucs = 'Cu';
Sys.gStrain = [0.100929 0.0175188 0.0855639];
Sys.gAStrainCorr = -1;

Opt.Verbosity = 1;
Opt.Method = 'Matrix';

SysVary.g = [0.04 0.025 0.025];
SysVary.A = [30 20 50]
SysVary.gStrain = [0.2 0.2 0.2];

esfit(spc1,@pepper,{Sys,Exp,Opt},{SysVary})

hi,
you should read this: https://easyspin.org/forum/viewtopic.php?t=179
Otherwise, did you first perform global fit (Genetic) before local (simplex or levenberg)?
Emilien

Hi Emilien,

Thank you for the link. I have read that one in the past. You'll see I have included the anticorrelated strain parameter in the simulation. Although I am realizing now that I have forgotten to paste the A-strain values into my initial post, I did include them in the fit shown.

And for the fit, it was done using a local simplex. The initial g and A (at least for A||) parameters were the observed g and A values, which yielded a pretty close fit already. Perhaps I should try a global fit for the strain though, since the g values seem accurate?

Thanks,

Macon