Spatially resolved two-dimensional Fourier transform electron spin resonance

In the accompaning Letter [ I] we have described successful FT-ESR imaging experiments utilizing pulsed field gradients. It was shown that the phase encoding method is the preferred one, and it yields spectral-spatial images of a quality comparable to the best cw-ESR spectral-spatial images even though it is only at an early stage of development. The realization of these FT-ESR imaging experiments opens up a range of new possibilities. One is the possibility of performing spatially resolved ESR spectroscopies based upon modem FT methods. In particular, we shall emphasize in this Letter spatially resolved two-dimensional electron-electron double resonance (2D-ELDOR) [2-71. 2D-ELDOR is a form of 2D-exchange spectroscopy that is very sensitive to cross-relaxation processes including Heisenberg spin exchange (HE) and nuclear spin flips induced by electron-nuclear dipolar interactions. They are important measures of microscopic translational diffusion, and rotational diffusion respectively. Spatial resolution would, for example, permit one to