Transition in 'xy' direction missing

[Heiko]

Hi,

I am not sure if this is a possible bug or if I'm just missing something.

I simulated a spectrum which reproduces my experiment quite well, though one transition is missing.
However, checking with the levelsplot function tells me the transition is there and allowed.

In the region between 7 and 10 T there are two transitions (x and y directions according to levelsplot) from the 3rd to 4th level.
In between should be an additional transition according to the xy-levelsplot (originating from the same level) which I see in my measurement but is missing in the simulated spectrum.
Unfortunately, it looks like I cannot attach a picture to show my point.

To be safe, I increased the number of points and knots but this did not help.
I am using EasySpin 5.2.25 with Matlab 2018b.

The (hopefully) working code is here:

Code: Select all

clear, clc

Sys.S = 2;
Sys.g = [2.22 2.01 2.1];
D = -3.29;
E = 0.22;
Sys.D = [D E]*clight/10000;
Sys.gStrain = [0.05];

frequencies_exp = 320;

Exp = struct('Temperature',12,'mwFreq',frequencies_exp,'Range',[0 15500],'Harmonic',1,'nPoints',4096);

Opt.nKnots = 91; %Standard: 19

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

y_meanvalue = mean(y);
y_mean = y - y_meanvalue;

%%
figure(1)
clf
set(gcf, 'Color', 'w');
set(gca,'LooseInset',get(gca,'TightInset'));

subplot(5,2,1)
xlim([0 15]);
hold on
ax = gca;
ax.ColorOrderIndex = 1;
plot(x/1000,y_mean,'-');
xlim([0 15])
ylim([-5e-4 8e-4])
hold off

subplot(5,2,2)
xlim([0 15]);
hold on
ax = gca;
ax.ColorOrderIndex = 1;
plot(x/1000,y_mean,'-');
xlim([0 15])
ylim([-5e-4 8e-4])
hold off

subplot(5,2,3)
levelsplot(Sys,'x',[0 15000],frequencies_exp)
title('')
xlabel('')
ylabel('')
axis tight
title(['x, ',num2str(frequencies_exp),' GHz'])

subplot(5,2,5)
levelsplot(Sys,'y',[0 15000],frequencies_exp)
title('')
xlabel('')
ylabel('')
axis tight
title(['y, ',num2str(frequencies_exp),' GHz'])

subplot(5,2,7)
levelsplot(Sys,'z',[0 15000],frequencies_exp)
title('')
xlabel('')
ylabel('')
axis tight
title(['z, ',num2str(frequencies_exp),' GHz'])

subplot(5,2,4)
levelsplot(Sys,'xy',[0 15000],frequencies_exp)
title('')
xlabel('')
ylabel('')
axis tight
title(['xy, ',num2str(frequencies_exp),' GHz'])

subplot(5,2,6)
levelsplot(Sys,'xz',[0 15000],frequencies_exp)
title('')
xlabel('')
ylabel('')
axis tight
title(['xz, ',num2str(frequencies_exp),' GHz'])


subplot(5,2,8)
levelsplot(Sys,'yz',[0 15000],frequencies_exp)
title('')
xlabel('')
ylabel('')
axis tight
title(['yz, ',num2str(frequencies_exp),' GHz'])


subplot(5,2,9)

set(gca,'visible','off');
subplot(5,2,10)
levelsplot(Sys,'xyz',[0 15000],frequencies_exp)
title('')
ylabel('')
axis tight
title(['xyz, ',num2str(frequencies_exp),' GHz'])

Is this a bug or am I missing something?
Thank you for your help.

Heiko

[Stefan Stoll]

In a powder spectrum, there is generally no feature along the 'xy' direction. The only features are along 'x', 'y', and 'z', which are the principal values of the D and g tensors in your system.

You can look at all the transitions separately:

Code: Select all

clear, clc

Sys.S = 2;
Sys.g = [2.22 2.01 2.1];
D = -3.29;
E = 0.22;
Sys.D = [D E]*clight/10000;
Sys.gStrain = [0.05];

Exp.Temperature = 12;
Exp.Range = [0 20e3];
Exp.mwFreq = 320;
Exp.nPoints = 4096;
Exp.Harmonic = 0;
Opt.nKnots = 91;
Opt.Threshold = 0;
Opt.Output = 'separate';
%Opt.Transitions = [3 4];
Opt.Verbosity = 1;

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

clf
plot(x,y);

[Heiko]

Thank you for the fast clarification!