Radio-frequency-driven electron spin echo envelope modulation spectroscopyon spin systems with isotropic hyperfine interactions

Three-pulse radio-frequency (rf) driven electron spin echo envelope modulat ion (ESEEM) is introduced as a method to measure hyperfine couplings of ele ctron-nuclear spin systems in liquids. It is distinguished from the corresp onding two-pulse experiment by narrower lines. Numerical simulations of rf- driven ESEEM based on Floquet theory are given and compared with average Ha miltonian theory. Artifacts which appear in rf-driven ESEEM spectra are dis cussed, and approaches for the removal of these artifacts such as time-prop ortional phase incrementation (TPPI) of the rf phase and an rf phase cycle (0, pi) are presented. The validity of the analytical description of the rf -driven ESEEM experiment is shown by comparison with experimental results. (C) 2001 American Institute of Physics.