I have an EPR spectrum where two individual radical spins (no coupling) exist with hyperfine coupling in a donor-acceptor system.

How can I convert the current spectrum to a situation where the two spins are coupled with each other?

Which parameters (exchange, dipolar coupling etc) are important while coupling the two spins?

I'm just a beginner in EPR acquisition and simulation, any help in this direction would be appreciated.

- Code: Select all
`clear`

%Experimental spectrum

[B,spc] = eprload('Exp');

%Spin A(acceptor):

SysA.S = 1/2;

SysA.g = [2.00986];

SysA.Nucs = '14N,1H,1H,1H,1H';

SysA.A = [1.74,4.810,2.2,1.63,0.36];

SysA.weight = 2.50;

SysA.lwpp = [0.6];

VaryA.A = [0.1,0.1,0.1,0.1,0.1];

VaryA.g = [0.5];

VaryA.lwpp = 0.5;

VaryA.weight = 0.3;

%Spin D (donor):

SysD.S = 1/2;

SysD.g = [2.009967];

SysD.weight = 0.908;

SysD.lwpp = [0.15566];

SysD.Nucs = '1H,1H,1H,1H,1H';

SysD.A = [18.81675,9.0468,3.9166,8.46,4.16];

VaryD.A = [0.2,0.2,0.2,0.2,0.2];

VaryD.g = [0.5];

VaryD.lwpp = 0.5;

VaryD.weight = 0.3;

%Defining the two spins together:

Sys = {SysD SysA};

Vary = {VaryD VaryA};

%Experimental details:

Exp.mwFreq = 9.452387;

Exp.Range = [320.873 350.873];

Exp.nPoints = 65536;

Exp.ModAmp = mhz2mt(0.1); %in mT

Exp.Temperature = 298; %in Kelvin

Exp.Mode = 'perpendicular';

B = linspace(Exp.Range(1),Exp.Range(2),Exp.nPoints);

% Calling the fitting function

%SimOpt.nKnots = 35;

SimOpt.Method = 'perturb';

FitOpt.Method = 'simplex fcn'; % simplex algorithm,

%FitOpt.Scaling = 'maxabs';

[fitparams,spc] = esfit('pepper',spc,Sys,Vary,Exp,SimOpt,FitOpt);

hold on;

%Loading experimental spectrum.

data=textread('Exp_Spec.dat');

x=data(:,1);

y=data(:,2);

plot(x,y,'k');

%Saving in ascii format

data = [B(:) spc(:)];

save('Code_ES_Sim.dat','data','-ascii');

plot(B,spc,'r');

hold off;

Please help if possible.