A Rigorous Procedure for Calculation of Pulsed EPR Signals with Relaxation

A procedure is developed to calculate pulsed electron paramagnetic resonance (EPR) signals with relaxation rigorously. It can be carried out within a reasonable time on a PC using Fortran or Matlab, not requiring any sophisticated software. The flow chart for this kind of simulation is included. It is illustrated here numerically, as coded in Matlab, to calculate the two- dimensional spin echo correlation spectroscopy (2D-SECSY) and two-dimensional electron-electron double-resonance (2D-ELDOR) signals for two cases: (i) a coupled electron-nuclear system with the electron spin (S= ½) and nuclear spin (I= ½) corresponding to the experimental results of Lee, Patyal and Freed [1] in a malonic acid single crystal, and (ii) 2D-ELDOR signal obtained for an electron-electron dipolar-coupled system of two nitroxide radicals in a malonic acid single crystal, with hyperfine interactions included, for a proposed experiment, intended for distance measurements, important for biological systems. The limits of applicability of the algorithm used here are discussed.