Nucleus-nucleus interaction Hamiltonian.

F = ham_nn(Sys)
F = ham_nn(Sys,nucSpins)
F = ham_nn(Sys,nucSpins,'sparse')

ham_nn returns the nucleus-nucleus interaction part of the spin Hamiltonian of the spin system given in Sys, in units of MHz.

In the spin system structure, the fields nn and nnFrame parametrize the nucleus-nucleus interaction.

If the vector nucSpins is specified, only the interactions between the nuclei listed in nucSpins is computed. For example, if nucSpins = [1 3], only the interaction between nucleus 1 and nucleus 3 is returned. Otherwise, all nuclei are included.

If 'sparse' is given as third argument, the Hamiltonian matrix is returned in sparse format, instead of full format.

For a system with one electron and two nuclei

Sys.S = 1/2;
Sys.Nucs = '1H,1H';
Sys.nn = [1 1 -2]*0.04;   % MHz
Sys.A = [10 12];          % MHz

the nucleus-nucleus coupling Hamiltonian (in MHz) is

nnHam = ham_nn(Sys)

nnHam =
   -0.0200         0         0         0         0         0         0         0
         0    0.0200    0.0200         0         0         0         0         0
         0    0.0200    0.0200         0         0         0         0         0
         0         0         0   -0.0200         0         0         0         0
         0         0         0         0   -0.0200         0         0         0
         0         0         0         0         0    0.0200    0.0200         0
         0         0         0         0         0    0.0200    0.0200         0
         0         0         0         0         0         0         0   -0.0200

ham, ham_cf, ham_ee, ham_ez, ham_ezho, ham_hf, ham_nq, ham_nz, ham_oz, ham_so, ham_zf