Quantum interference phenomena in the local polarization dynamics of mesoscopic systems: an NMR observation

It has been predicted that local spin polarization in a ring of five dipolar coupled spins should present a particular fingerprint of quantum interferences, reflecting both the discrete and finite nature of the system. We report its observation for the proton system of a (C5H5)2Fe molecule using the rare 13C as local probe. Novel high frequency (≈ 60 kHz) polarization oscillations appear because incomplete 13C1H cross-polarization transfer splits the polarization state into a portion that wanders in the proton system and one that remains in the 13C. They interfere with each other after rejoining.