Extension of the accessible dynamical range of reorganization in ESEEM simulations of single crystals

An appropriate theory for studying the effects of exchange rearrangements on ESEEM signals is developed using the density operator directly in Liouville space. Primary echo simulations in single crystals are studied in detail in this work. The effect of exchange on ESEEM in the fast motion limit is an averaging of the rigid limit frequencies as in ESR lineshapes. For intermediate rates almost all structure disappears from the ESEEM spectrum and the simple linear relation TM α k±1 between the phase memory time TM and the exchange rate k is found to be valid. The exponential intrinsic relaxation rate due to other processes than exchange adds to the phase memory decay rate in a simple way. We suggest a quantitative method of using the decaying time domain signals of the intermediate exchange region. In comparison to the dynamical range of other magnetic resonance methods, the ESEEM seems to be superior and ideally lifetimes in the interval 10−11−10−1 s become accessible.