Polarization transfer in multispin systems driven by a recoupled zero-quantum dipolar Hamiltonian has been investigated theoretically and experimentally. It was shown by computer simulations and supported experimentally that having started at a particular nucleus, polarization propagates through the whole cluster of strongly coupled spins, reaching a quasi stationary state that depends on the initial conditions. Perturbation theory has been used to show that polarization exchange between weakly coupled clusters of strongly coupled spins can be expected to occur only for special cases and is driven by internal resonances. In powder samples, the transfer of polarization was found not to be sensitive to the structure and/or conformation of the spin system due to orientational averaging. However, the possibility is being explored to suppress this effect by modifying the recoupled Hamiltonian and/or by creating an orientation-dependent initial states. In order to perform the highly demanding computations involved in the problem, fast and effective software and hardware are essential. To this end, a special computer program has been developed. It is utilizing an original approach to integration of the Schrodinger equation with time-dependent Hamiltonian. A new Gaussian-type interpolative algorithm is also being developed to perform powder averaging. The current research is directed towards creating a new technique for simultaneous measurement of multiple distances in uniformly or multiply labeled compounds and is important for better understanding of coherent processes in these systems.
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