Multiquantum ODMR spectroscopy of semiconductors and silver chloride

Strong signals corresponding to electron paramagnetic resonance (EPR) transitions with the absorption of two, three and so on microwave quanta have been observed in optically detected magnetic resonance (ODMR) spectra of bulk semiconductors (A2B6, SiC), type-II GaAs/AlAs superlattices and silver chloride crystals. Multiquantum ODMR spectroscopy was applied to analyse the energy levels of Al, Ga and Sc accepters in silicon carbide and showed a nonlinearity of the energy levels of Sc acceptors in a magnetic field. In ASCI crystals, multiquantum ODMR of self-trapped holes, electrons and self-trapped excitons was found. For the first time, multiquantum ODMR was observed between fine-structure energy levels, i.e. for a system with electron spin S>1/2. Singlet-to-triplet multiquantum EPR transitions with absorption of up to seven microwave quanta were detected for self-trapped excitons and unambiguously identified by frequency shift measurements. The singlet-to-triplet splitting has been determined with a very high accuracy: J=-161.0+or-0.1 GHz.