| Popis: |
In solids containing both unpaired electrons and nuclear spins, the dynamic nuclear polarization (DNP) technique can be applied to enhance the NMR signal. DNP requires irradiation at or near the electron Larmor frequency, and in this paper two probes are described to achieve this goal. Two new DNP probes were designed for electromagnets operating at a field of 1.4 T. In one probe, DNP can be combined with CPMAS. Compared to a similar probe reported previously, the main advantage of the new probe is the capability to spin vacuum-sealed samples with an improved filling factor. A second probe is based on an oversize microwave cavity. In this probe, large DNP enhancement factors can be obtained in nonlossy samples, e.g., a 1 H enhancement factor of 260 for doped polystyrene. |
