Ten transitions in the fundamental band of the FeH radical in its grou
nd 4DELTA state have been detected by CO laser magnetic resonance. Ass
ignments of the M(J) structure have been made for each transition and
the parameters of an empirical energy level model have been determined
. This method has allowed zero-field transition wavenumbers to be dete
rmined very accurately, as well as g factors for FeH in the v = 1 leve
l.