Analytical expression for a DEER trace for two spins in the presence of dipolar and exchange (EPR) or J (NMR) coupling. This function returns the powder averaged dipolar modulation signal in DEER, PELDOR and in-phase ESEEM type experiments, as well as in solid state NMR spectroscopy where dipolar modulation has been isolated by selective recoupling.
D - dipolar coupling, angular frequency units, the coefficient in front of (1-3*cos(theta)^2)*Lz*Sz in the spin Hamiltonian J - exchange coupling, angular frequency units, NMR convention (no factor of 2 in front), the coef- ficient in front of Lz*Sz in the spin Hamiltonian t - array of time points, seconds
deer - an array of DEER form factor values of the same dimension as t
See examples/esr_solids directory for multiple examples from EPR spectroscopy.
- Distance distributions in real molecules are rarely delta functions. If the distribution has a width, it would impose and additional exponential or Gaussian decay on the modulation produced by this function.
- The presence of observer spins can generate a background signal that may be approximately described by a stretched exponential.
Version 2.2, authors: Ilya Kuprov