Electron nuclear double resonance spectroscopy.

Precise information about the molecular structure, stereochemistry, and environment of paramagnetic species can be obtained by electron nuclear double resonance (ENDOR) spectroscopy. This technique has been applied in a wide range of disciplines to liquid-phase, single-crystal, and powder samples. In some cases-the study of defects in ionic single crystals, for instance-the volume and complexity of data obtained by ENDOR can hinder interpretation. Such difficulties have been overcome by the use of supplemental ENDOR techniques that simplify the assignment of ENDOR lines. The increased use of computers for the automation of instrumentation, the design of experiments, and the analysis of data has made possible the study of a wider range of problems. With these improvements, as well as with the increased sensitivity provided by optically detected ENDOR, it is now feasible to study polycrystalline and amorphous materials, such as thin-film semiconductors and biological samples in vivo.