Pulse EPR

This is a short introduction to the principles of pulse EPR spectroscopy, intended for the reader who is already familiar with continuous-wave (CW) EPR. After an initial comparison of pulse EPR to CW EPR, the basics of pulses and their effects on electron spins are discussed. Then, the basic pulse sequences (one, two, and three pulses) and the associated signals (free induction decay, primary echo, and stimulated echo) are introduced. The effects of spectral, pulse, and resonator bandwidths are considered together with the resulting orientation and transition selection. Non-coherent effects including longitudinal and transverse spin relaxation, phase memory time, spectral diffusion, and instantaneous diffusion are discussed. After a brief explanation of the workings of a pulse EPR spectrometer based on a block diagram and discussion of resonator ringdown, deadtime, and phase cycling, this introduction concludes with some practical aspects relevant to performing pulse EPR experiments.