ABSTRACT
Numerous electron nuclear double resonance (ENDOR) investigations of radicals in solution have shown that the ENDOR spectrum is sensitive to the environment of the radical, such as temperature, viscosity, oxygen concentration, and the kind of nucleus detected. Since ENDOR spectroscopy detects the nuclear magnetic resonance (NMR) spectrum of a paramagnetic species, one could imagine producing an image similar to that of a NMR image. The ENDOR cavity used is 4.8 cm wide; a pair of figure-eight coils is constructed so as to fit into the remaining space between the cavity and the magnet pole. ENDOR projections were collected by rotating the field gradient within the xy-plane, and the two-dimensional image was constructed. Slices of stems of a house plant, Tradescantia, were subjected to ENDOR-detected imaging to find the difference in oxygen concentrations in different portions of the stem. The ENDOR intensity of a spin probe is a sensitive function of the temperature, as well as the viscosity, of the environment.
