Field Cycling by Fast NMR Probe Transfer:Design and Application in Field-Dependent CIDNP Experiments

摘要

A novel field-cycling unit with fast digital positioning of a high-resolution unclear magnetic resonance probe in a spatially varying magnetic field is described and used to measure CIDNP spectra of the amino acid-dye (histidine-bipyridyl) photoreaction system in the range between 0 and 7 T. The pattern of nuclear polarization varies with the magnetic field. In particular, strong polarization with an emission/absorption pattern (multiplet effect) is found at low field for two histidine ringprotons with scalar coupling below 3 Hz visible only because of the high resolution made possible by the new field-cycling setup. Also for the CH_2 protons in the #beta#-position a multiplet effect is observed having a pattern changing with magnetic field. By analysis of the spin nutation the nonBoltzmann population differences of the nuclear levels have determined.