Right-angle spinning for sensitivity improvement in pulse EPR experiments

Right-angle spinning EPR, in which the sample is rotated about an axis perp endicular to the static magnetic field, is introduced for improvement of th e sensitivity of pulse EPR experiments on orientationally disordered system s. Often the rang of excitation of the microwave pulses is much narrower th an the spectral width, so that only a small fraction of the spins is involv ed in the experiment. Under right-angle spinning these spins are shifted of f-resonance and spins still in thermal equilibrium become resonant, resulti ng in an increase in repetition rate and thus in sensitivity. The principle s of the new approach are described, and experiments are presented in which the measuring time is found to be reduced by a factor of more than 200. (C ) 1999 Elsevier Science B.V. All rights reserved.