Decoherence during 1H-13C Cross Polarization

GONZALO A. ÁLVAREZ; ERNESTO P. DANIELI; PATRICIA R. LEVSTEIN; HORACIO M. PASTAWSKI

San Carlos de Bariloche, Argentina

Workshop; Pan American Advanced Studied Institute (PASI) on Physics at the Nanometer Scale - PASI 2003; 2003

Pan American Advanced Studied Institute

We present a model for the quantum evolution of a coupled nuclear spin system 13C-1H connected to a reservoir. There, the decoherence is introduced by stroboscopically (and then continuously) stopping the quantum evolution. Polarization is injected to the system at each step of the interrupted evolution with certain probability. Excellent agreement with experimental data taken in molecular crystals and liquid crystals is observed. It is noticeable that this simple model produces the exact result that can be obtained by reintroducing the neglected non-secular terms in the generalized Liouville-von Neumann approach introduced by Müller et al. [Phys. Rev. Lett. 32 (1974) 1402]. Thus, it is possible to establish the equivalence of these approaches and gain in the understanding of the physical significance of each contribution to the evolution, i.e. the part that produces dissipation and that inducing only decoherence.