Unexpected powder spectra after rotation of reference frames
Posted: Fri May 25, 2018 6:31 am
Dear all,
I am performing some preliminary test to simulate spectra of an exchange-coupled pair of largely anisotropic effective doublets. The relevant hamiltonian is then H= B(g1*S1+g2S2)+JS1S2+S1DS2.
When simulating the powder spectrum with the code I include below I got two different patterns if I rotate the reference frames of all the anisotropic interactions in the same way (i.e. gFrame1=gFrame2=DFrame), see figure. I am sure I am missing something here, because in principle what I would like to do is a simple change of reference frame which should not affect the powder spectrum.
Any help would be welcome.
I am performing some preliminary test to simulate spectra of an exchange-coupled pair of largely anisotropic effective doublets. The relevant hamiltonian is then H= B(g1*S1+g2S2)+JS1S2+S1DS2.
When simulating the powder spectrum with the code I include below I got two different patterns if I rotate the reference frames of all the anisotropic interactions in the same way (i.e. gFrame1=gFrame2=DFrame), see figure. I am sure I am missing something here, because in principle what I would like to do is a simple change of reference frame which should not affect the powder spectrum.
Any help would be welcome.
Code: Select all
clear all
convfact=clight/1e4; %cm-1 to MHz
testaniso.S = [1/2 1/2]
testaniso.g = [4.16 1.52 1.08;4.16 1.52 1.08]; % g, for two electron spins
testaniso.J=-0.08*convfact;
testaniso.eeD =[-0.16 0.08 0.08]*convfact;
testaniso.lw=[10 10];
testaniso.HStrain=[700. 700. 700.];
Exp=struct('mwFreq',94.3,'nPoints',8192,'Range',[10 7500],'Temperature',10,'Harmonic',1); %campo in mT
Opt.nKnots=[91 3]
[B1,spec1] = pepper(testaniso,Exp,Opt);
figure('Name','Spectrum','NumberTitle','off');
testaniso.gFrame=[-15*pi/180 90*pi/180 -0*pi/180;-15*pi/180 90*pi/180 -0*pi/180]
testaniso.eeDFrame =[-15*pi/180 90*pi/180 -0*pi/180]
[B2,spec2] = pepper(testaniso,Exp,Opt);
plot(B1,spec1/max(spec1),'g',B2,spec2/max(spec2)+0.1,'r','LineWidth',2);
xlabel('magnetic field (mT)');
ylabel('Signal');