ANOMALOUS EXCITATION IN THE ESR-SPECTRUM OF THE FE3+ ION IN GAAS

The observation of anomalous intensities of lines in the ESR spectrum of a Fe3+ center in GaAs is reported. Two lines in the spectrum of the S=5/2 spin system, which correspond to the transitions M(S) = -5/2<-> -3/2 and M(S) = - 3/2<-> -1/2, have anomalously high intensities. It is shown that this effect is produced by the electric quadrupole excit ation acting in addition to the magnetic-dipole mechanism. The contrib ution of the orbital angular momentum from the excited states, which m akes this mechanism possible for ions in a singlet orbital ground stat e, is discussed. (C) 1996 American Institute of Physics.