Novel analytical treatments of electron spin-echo envelope modulation with short and extended pulses

Abstract

The analytical description of two-pulse electron spin-echo envelope modulation experiments is extended by the derivation of two generalized expressions for the echo amplitude. At first, the effect of a variable position of the observer window is computed for delta function pulses. A new type of peak suppression effect, the so-called “observer blind spots,” is discussed. Second, a novel procedure for handling pulses of extended length is introduced. It is based on a pulse representation in terms of a sequence of pulse slices and leads to the first analytical expression that correctly describes an ESEEM experiment performed with pulses of any length, provided the EPR linewidth is much larger than the inverse pulse length. The predicted features are verified experimentally, in particular, the formation of blind spots and the influence of the position and the duration of the observer window.