Imaging electromagnetic fields using the magnetic resonance absorption spectrum of a paramagnetic gas

The magnetic component of an electromagnetic field confined to a cavity resonator operating in the 3.2 cm wavelength region has been mapped using the noninvasive technique of electron paramagnetic resonance imaging. The active agent used for this purpose was molecular oxygen. One- and two-dimensional images were obtained of the fields in each of two distinct cylindrical cavity resonators. These images were found to correspond to the general features of those predicted by waveguide theory. © 1988