EasySpin forum

I am a bit confused about how to specify the nuclei and corresponding hyperfine constants in Easyspin for a biradical where each of the two electrons interacts with its own set of nuclei. How should I write the Sys.Nucs and Sys.A variables so as to specify nuclei interacting with electron 1 and nuclei interacting with electron 2?
Thanks for your help.

Laurent Binet
Chimie-ParisTech

For one nuclear spin per electron spin, the general format, including superhyperfines would be:
Sys.A = [A11 A12; A21 A22]

To exclude the superhyperfines, thus only each nuclear spin with its own electron:
Sys.A = [A11 0; 0 A22]

Note that Aij can be scalars (isotropic hf), 1x2 vectors (axial hf), 1x3 vectors (rhombic hf) and you may want to define Sys.AFrame as well. Otherwise they can be 3x3 matrices when you define the A-tensor explicitly. Of course, the "zeros" in all these cases would need to have the same format.

In both cases the nuclei would be just the two you want:
E.g.
Sys.Nucs = '14N,14N'

*If you have more nuclei, you add one line per nucleus to Sys.A.

Thanks so much Thanasis. It helped.

Laurent

Hi Thanasis

im in a similar situation and I'm sort of stuck

how does one specifically differentiate the hyperfine for three equivalent nuclei?

example Sys.Nucs = '14N,14N,14N, for a benzotriazinyl radical . it is known that two of coupling constants have values very close to each other . is there a way to note specific coupling constant for each nuclei?

also are you reachable via any other means other than here?

If there is only a single electron spin, the second column is not needed, just a third line. You only make two of the three lines equal. E.g.
Sys.A = [A1; A2; A2]

The same as before applies to the format of A1/A2.

Hi Thanasis

i kind of understood what you mean but I'm still not very clear.
i do have a single electron spin and my code looks like this
Sys.Nucs = '14N, 14N, 14N';
Sys.A = [21.5, 14.8, 13.7]

i have 3 equivalent nitrogen with different IUPAC numbering (N1, N2, N4)- im not sure if hyperfine 14.8 belongs to N2 or N4
between the last two nitrogens, i can't tell which is which

i don't know if easy spin has a function that allows me differentiate between the three equivalent nitrogen specifically

[B,spc] = eprload('6_AminoBTR_30_08_23.DTA');
plot(B,spc);
Exp.mwFreq = 9.369752;
Exp.Range = [324.935 344.925]; % mT
Exp.nPoints = 2000; %numel(B)
%Exp.ModAmp = 0.1;
Exp.Temperature = 298;
% Set up spin system with starting parameters
Sys.g = 2.0036;
Sys.S = 1/2;
Sys.Nucs = '14N, 14N, 14N';
Sys.A = [21.5, 14.8, 13.7]; %MHz
Sys.lwpp = [0.35 0.15];
% Set up Vary structure with all parameters that can be varied
Vary.g = 0.002;
Vary.lwpp = [0.02 0.05];
SysVary.A = [5, 5, 5];
Vary.A = [2, 2, 2];

The way your code is written, the three hyperfines are independent.

To tie two of the variables to the same value, you will need to pass through a custom function.

Take a look at this old post: https://easyspin.org/forum/viewtopic.php?p=863#p863