On cubic ZnS crystals doped with Fe the paramagnetic resonance spectru
m of a monoclinic Fe-Zn(+)(A(-))-X complex with a (4)A(2)(F) ground st
ate has been studied under band to band illumination. The monoclinic d
istortion of the cubic crystal held is due to one or more associated d
efects ''X'' whose origin remains unknown. The largest component of th
e distortion is oriented along a [100] axis. All transitions arise fro
m a spin ground doublet \ +/- 1/2] which can be described by an effect
ive spin Hamiltonian with S' = 1/2. The g'-values are g'(z') = 2.223,
g'(x') = 4.426, and g'(y') = 4.608 with x' being [110] and y', z' incl
ined about 8.5 degrees against [($) over bar 110] and [001], respectiv
ely, in the plane perpendicular to x'. The corresponding parameters of
a spin Hamiltonian describing the full S = 3/2 (d(7)) ground state ma
nifold are g(x') = g(y') = 2.259, g(z') = 2.224 and E/D = 0.0134 with
D > 1 cm(-1).