# eigenfields.m

From Spinach Documentation Wiki

Computes resonance fields. For a Hamiltonian Hc+b*Hz, returns all magnetic fields b for which the difference between any two eigenvalues of Hc+b*Hz is equal to omega.

## Syntax

[b,uv]=eigenfields(Hc,Hz,omega,window)

## Arguments

Hc - laboratory frame Hamiltonian commutation superoperator containing all spin-spin couplings, but no Zeeman interactions Hz - laboratory frame Hamiltonian commutation superoperator containing Zeeman interac- tions at 1 Tesla omega - resonance frequency in rad/s window - frequency window to consider, a vector with two elements, rad/s

## Outputs

b - vector of magnetic fields in Tesla uv - a matrix of |u><v| dyadics where |u> and |v> are separated by omega under Hc+b*Hz

## Notes

A very expensive and barely stable generalised eigensolver supplied with Matlab is used.

## See also

*Version 2.3, authors: Ilya Kuprov*