High Quality Content by WIKIPEDIA articles! Electron nuclear double resonance (ENDOR) is a magnetic resonance technique for obtaining detailed molecular and electronic structure of paramagnetic species. In the standard continuous wave (cwENDOR) experiment, a microwave field is first applied, followed by irradiation with a radio frequency field. The changes are then detected by monitoring variations in the polarization of the saturated electron paramagnetic resonance (EPR) transition. George Feher introduced this technique in 1956 so that interactions which are not accessible in the EPR spectrum could be resolved.