# eigenfields.m

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.