transition simulation

[siavash.saeidpour]

I tried to simulate the transition spectra of nitroxide at different frequencies (S-, X-, Q- and W- band). But the shape of spectra at W-band is not similar to expected form. (especially M_{I}=0 transition).

ExpS = struct('Range',[120 130 ],'mwFreq',3.5 ,'Harmonic',0,'nPoints',2048,'Temperature',80);
ExpX = struct('Range',[330 340 ],'mwFreq',9.4 ,'Harmonic',0,'nPoints',2048,'Temperature',80);
ExpQ = struct('Range',[1240 1255 ],'mwFreq',35 ,'Harmonic',0,'nPoints',2048,'Temperature',80);
ExpW = struct('Range',[3335 3365 ],'mwFreq',94 ,'Harmonic',0,'nPoints',2048,'Temperature',80);
N.Nucs = '14N';N.g = [ 2.01 2.006 2.002]; N.A = [ 15 15 100];N.lwpp= 0.8;
Opt = struct('Output','separate');
Opt.Transitions = [1 6;2 5; 3 4];
%% S-band
[simBS,simSpcS]=pepper(N,ExpS,Opt);
[simBSS,simSpcSS]=pepper(N,ExpS);
%% X-band
[simBX,simSpcX]=pepper(N,ExpX,Opt);
[simBXS,simSpcXS]=pepper(N,ExpX);

%% Q-band
[simBQ,simSpcQ]=pepper(N,ExpQ,Opt);
[simBQS,simSpcQS]=pepper(N,ExpQ);

%% W-band
[simBW,simSpcW]=pepper(N,ExpW,Opt);
[simBWS,simSpcWS]=pepper(N,ExpW);

[Stefan Stoll]

At W-band, there is strong mixing of the nuclear spin levels via the hyperfine coupling (it's called the cancellation regime). Therefore, there are more than 3 transitions with significant intensity. If you comment out the Opt.Transitions line, you will see that.