Spectral spatial EPR imaging with modulated gradient and simultaneous field scan (MOSS) was investigated with regard to its spectral and spatial resolution and its total measuring time. The gradient coil system is used to overlap the fast field scan with a modulated field gradient. The complete image was measured in 64 s, utilizing a gradient-modulation frequency of 66 s−1. This technique does not require image reconstruction. The influence of different modulation functions (cosine and triangular) and of a partial blanking of the applied cosine-modulated signal on the spectral-spatial image is discussed. The partial-blanking method is most suitable for fast imaging and best image quality.

Fourier transform ESR methods have been extended to permit spatially resolved two-dimensional (2D)-ESR experiments. This is illustrated for the case of 2D-electron-electron double resonance (2D-ELDOR) spectra of nitroxides in a liquid that exhibits appreciable cross-peaks due to Heisenberg spin exchange. The use of spin-echo decays in spatially resolved FT-ESR is also demonstrated.

The macroscopic and the microscopic diffusion coefficients of a phospholipid spin label (16-PC) in the model membrane 1-palmitoyl-2-oleoyl-sn-glycero-phosphatidylcholine have been measured simultaneously in the same sample utilizing the new technique of spectral-spatial electron spin resonance imaging. The macroscopic diffusion coefficient D(macro) for self-diffusion of 16-PC spin label is obtained from imaging the concentration profiles as a function of time, and it is (2.3 +/- 0.4) x 10(-8) cm2/s at 22-degrees-C. The microscopic diffusion coefficient D(micro) for relative diffusion of the spin probes is obtained from the variation of the spectral line broadening with spin label concentration, which is due to spin-spin interactions. D(micro) is found to be substantially greater than D(macro) for the same sample at the same conditions, and is estimated to be at least (1.0 +/- 0.4) x 10(-7) cm2/s. Possible sources for their difference are briefly discussed in terms of the models used for D(micro).

Modern Fourier transform (FT) ESR methods have been combined with fast, high power pulsed magnetic field gradients to enable FT-ESR imaging. Spectral—spatial imaging by frequency and phase encoded FT methods are compared with cw methods. The initial phase encoded results are comparable in quality to those from the well-developed cw methods and further improvements which would enhance FT-ESR imaging are noted.

A mathematical formalism is presented for the analysis of EPR zeugmatograms measured using cosinusoidal or triangular modulated magnetic field gradients. The simulation of the 2D zeugmatograms, which depend on a spatial and a spectral coordinate, is based on a convolution of an ideal instrumental function and the spatial and spectral distribution of paramagnetic species. The mathematical model permits correction of the effect of the neighbor elements, which is a condition for a distortion-free image processing. The model described is demonstrated with a polyethylene cube containing spin probe solution.