Temperature effect on the intensities of simulation of ENDOR spectra

[Cleto]

Dear all,

I'm trying to simulate 14N Davies ENDOR spectra (X-band) of a Ni(I) complex. The ENDOR spectra were measured at two field positions: perpendicular (spectrum at the top) and parallel (spectrum at the bottom of the attached figures). I'm struggling a bit in getting the proper intensities of the experimental peaks. I noticed that the inclusion of the temperature in the simulation affects slightly the intensities of my simulation. In particular, a temperature of 10 K (same as the one emplyed for the experiments) and 298 K has a similar effect on the intensities of the simulated spectra. If I do not include the temperature in the simulation the intensities fit somehow better to the experimental spectra.
Does someone know the reason behind this?
Here there is the input I am using:

%% Davies ENDOR simulation 14N 1st species

clear, clc
[v(1,:),spc(1,:)] = eprload('MFU_3078_Davies_basecorr.DSC');
spc(1,:) = real(spc(1,:))/max(real(spc(1,:)));
[v(2,:),spc(2,:)] = eprload('MFU_3250Davies_basecorr.DSC');
spc(2,:)= real(spc(2,:))/max(real(spc(2,:)));

Exp.nPoints = 2048;
Exp.mwFreq = 9.75417;
Exp.ExciteWidth = 80;
Exp.Range = [1 30];
B = [307.8 325.0];
Exp.Temperature = 10;

Options = struct('GridSize',181,'Enhancement','on','OriPreSelect', 1);

for j = 1:1:2

Code: Select all

    Sys.S = 1/2;
    Sys.g = [2.136 2.167 2.270];
    %Sys.g = [2.145 2.260];
    Sys.Nucs = '14N';
    A1iso = 21; 
    T1 = [-2.0 -2.0 4.0];
    Sys.A = [A1iso + T1];
    Sys.Q = [3.9 0.8]
    Sys.AFrame = [0 90 0]*pi/180;
    Sys.QFrame = [0 5 15]*pi/180;
    
    Sys.lwEndor = 0.2;
    
    Exp.Field = B(j);
    
    
    [v_sim(j,:),spc_sim(j,:)]=salt(Sys,Exp,Options);
    spc_sim(j,:)=spc_sim(j,:)/max(real(spc_sim(j,:)));

end

for j = 1:1:2
plot(v(j,:),spc(j,:)+j*1.05,'k',v_sim(j,:),spc_sim(j,:)+j,'r','LineWidth',1)
hold on
end
xlim([2 30]) % left and right limits of the x-axis
xlabel('v / MHz') % x-axis label
ylabel('Signal Amplitude / a.u.') % y-axis label
h = gca;
h.YAxis.FontSize = 20;
h.XAxis.FontSize = 20;
hold off

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Thanks a lot for your help.

All the best,

cleto