University of Bath

Dept. of Physics

Basic principles of Optically Detected Magnetic Resonance

ODMR experiments rely on there being spin selection rules in the recombination process. As a result, the polarisation or the intensity of the emitted light depends on the population distribution in the spin levels of the excited state. Magnetic resonance transitions alter this spin distribution and can thus be detected by monitoring the transient changes that occur in the emission. In  ODMR studies of semiconductors, the information contained is similar in form to that provided by conventional ESR, and is normally expressed in terms of the parameters of a spin-Hamiltonian (for example, g-tensors, hyperfine splittings, crystal field splittings, exchange interactions). These parameters are very sensitive to the nature of the material, to the state of trapping, to local strains and to the degree of quantum confinement. ODMR has the further advantage over ESR in that the information is specific to the particular part of the light-emission process that is monitored.