EasySpin forum

In the following simplified example I find that switching from Opt.Method = 'hybrid' (or 'perturb2') to 'matrix'
(inclusion of nuclear Zeeman interaction) produces some small peaks a low frequencies.
I can not imagine how these should be related to an electronic spin flip.
Is this an artefact from the inclusion of the nuclear Zeeman interaction?

I would attach the files for the spectra if somebody showed me how to do this.

Sys = struct('S',1/2,'g',2,'lw',0.01);

Sys = nucspinadd(Sys,'9Be',[40 40 40]);

Exp.Field = 5;
Exp.mwCenterSweep = [0.15 0.3];
Exp.CrystalOrientation = [0 0 0];

Opt.Method = 'hybrid';

Opt.Verbosity = 1;

[x,y] = pepper(Sys,Exp,Opt);

x = x*1000;

plot(x,y,'b');
hold;

xlabel('Microwave frequency [MHz]');
ylabel('Normalised Intensity');

The four low-frequency lines you see are from the six nuclear transitions. With matrix diagonalization, they are found, but with perturbation theory, they are not included.

To see this, use the following after your code:

levelsplot(Sys,'z',[0 2*Exp.Field]);
xline(Exp.Field)

[frq,amp,~,transitions] = resfreqs_matrix(Sys,Exp);
resdata = [frq amp transitions];
sortrows(resdata)