A theoretical approach to the analysis of arbitrary pulses in magnetic resonance

We introduce split Hamiltonian theory (SHT) to analyze arbitrary pulses in magnetic resonance, i.e. pulses substantial in magnitude but not non-selective. The range of validity of the lower order approximations is discussed, and the method is illustrated by applying it to the consideration of pulse adjustable spectroscopies in time domain ESR that are utilized to study nuclear modulation. A virtue of SHT is that, whereas the approximate analytic solutions can provide useful insights, it can also be iterated numerically to achieve quantitatively accurate solutions.