EasySpin forum

Hello everyone,

I am currently trying to simulate a very complex spectrum of an organic radical that contains 4 nitrogens.

My current simulation is as follows:

clear, clf
Sys.g = [2.004];
Sys.Nucs = '14N,14N,14N,14N,1H,1H,1H,1H,1H,1H,1H';

Sys.E = 1
Sys.F = 0.8

A_N1 = [4]*Sys.E;
A_N2 = [12]*Sys.E;
A_H1 = [8]*Sys.F;
A_H2 = [0.5]*Sys.F;
A_H3 = [9]*Sys.F;
A_H4 = [0.8]*Sys.F;
A_H5 = [9.5]*Sys.F;
A_H6 = [0.6]*Sys.F;
A_H7 = [7]*Sys.F;

Sys.A = [A_N1;A_N1;A_N2;A_N2;A_H1;A_H2;A_H3;A_H4;A_H5;A_H6;A_H7];
Sys.lwpp = [0.005];



Exp.mwFreq = 9.85184;
Exp.Range = [348.5 354];
Exp.ModAmp = 0.03
Exp.nPoints = 11000

Opt.Method = 'perturb';
Opt.nKnots = [61 0];

[B2,spc1] = garlic(Sys,Exp,Opt);

spc2 = rescale (spc1, 'maxabs');

plot(B2,spc2,'b');

hold on

%[B,spc80] = eprload('N:\Projektübersicht\Projekt 4 Elektrolyse in der EPR-Zelle\Beckradikal\tert-NMepyAzin\tert NAzapz 091215\AB_tertNmepzazin_rt_modamp05_sample1_3');
[B,spc80] = eprload('N:\Projektübersicht\Projekt 4 Elektrolyse in der EPR-Zelle\Beckradikal\tert-NMepyAzin\tert NAzapz 091215\AB_tertNmepzazin_rt_modamp05_sample1_2');
C = (B)./10;
s81 = rescale(spc80, 'maxabs')

plot(C,s81,'r');

I have also tried to just fit it, but I guess my starting values are too far off.

My current approach is based on predicted values that I got out of a DFT calculation and the assumption that the absolut values may be off, but the ratio of the values is more or less correct.

I am sorry to bother you all, but I really don`t see how I can approach this simulation successfully. So, if anyone has a suggestion how I might do this, I would greatly appreciate it.

The one suggestion that I've got(and it may not help you at all) do you have access to cwENDOR? I've found in simulating these rather complicated spectra of organic radicals that the best approach is to fix some parameters to known values. cwENDOR provides one of those avenues, it gives you a way to measure directly the hydrogen couplings, well separated from everything else. Fix those and vary the nitrogen couplings.


Other notes, I tend not to use Exp.ModAmp but rather vary Sys.lwpp in my fitting, unless you're significantly over-modulating your spectrum both of those(ModAmp and lwpp) have similar effects on the spectrum.
Aside from that if you're confident in the ratio of values put together a custom fit function, vary Sys.E and Sys.F, and let esfit chew on it a while.