How to define inequivalent nuclei

[joematt]

Dear all,

I'm pretty new for EasySpin. Now I am trying to fit a spectrum of a Nitroxide solution using EasySpin 5.2.35, assuming it is isotropic and fast-motion one.

On each nitrogen hyperfine line, there is well-resolved proton hyperfine splitting. The protons are inequivalent. In the spin system, there should be a 14N nucleus, two 1H, four 1H, plus additional four 1H. So totally 2+4+4 = ten 1H.

My question is how do define such a spin system? Is the following correct?

[B,spc] = eprload('Z-3-0.5G-20dBBL.DTA');
spc1 = spc/(max(spc)-min(spc));
plot(B,spc1);axis tight

Exp.mwFreq = 9.5;
Exp.Range = [331,341];

Nx.S = 1/2;
Nx.g = 2.006;
Nx.Nucs = '14N,1H,1H,1H';
Nx.n = [1 2 4 4];
Nx.A = [55 8 4 2.2];
Nx.lwpp = [0.519 0.2];

Vary.A = [30 10 5 5];
Vary.lwpp = [0.519 0.2];
Vary.g = 0.02;

esfit('garlic',spc1,Nx,Vary,Exp);

I used the above statements but it cannot fit the spectrum well. The FitSpc just shows three main peaks from 14N hyperfine without any proton hyperfine splitting.

Thanks for very much for your help!

[thanasis]

In a system with C, H and N nuclei, the following had worked for me:

Code: Select all

Sys.Nucs = 'N,H,C';
Sys.n = [1,12,4];
Sys.A = [40.95 0.695 17.85]
Sys.lwpp = [0.0136 0.0203]

From a rapid glance, it seems you are on the right track. If I had to guess, I would say that your line widths are too large with respect to the 1H hyperfine couplings.

[joematt]

Dear Thanasis,

Thank you for the suggestion. It works...though still cannot fit the hyperfine structure very well no matter how.
Thanks a lot!

[Stefan Stoll]

I think the main issue with your original script is that the linewidths are larger than the hyperfine splittings, so the splittings are not resolved. Try reducting Sys.lwpp. Remember that Sys.A is in units of MHz, and Sys.lwpp in units of mT.