ELECTRON-SPIN-RESONANCE LINE-SHAPES FOR ONE-DIMENSIONAL AND 2-DIMENSIONAL RANDOM-WALK PROCESSES

One- and two-dimensional random walk processes and their effects on EP R (electron spin paramagnetic resonance) line shapes are examined. Dis crepancies between the coarse continuum model and the discrete hopping model are discussed. Closed-form formulas are prescribed for the dist ribution function, correlation (memory) function and the EPR line shap es, covering the entire range between the slow and the fast hopping li mits. Deviation from Gaussian or Lorentzian line shape is shown for in termediate hopping rates. Differences between the cases of a closed lo op and an open chain are illustrated. Time-domain analysis of line sha pe measurements can provide information about the hopping rate constan ts, site numbers in an open or closed chain, and the activation energy . (C) 1995 American Institute of Physics.