|The Role of Relaxation in NMR Signal Detection
by Stanislav Sykora (Extra Byte, Castano Primo, Italy), delivered at
the BFF6 2011 Workshop (Black Forest Focus on Soft Matter: Magnetic Resonance Microsystems),
organized by FRIAS, July 26-29, 2011, Saig (Freiburg), Germany.
See the program of this very good meeting.
This presentation introduces a somewhat contradictory topic bordering on the basic physics of the NMR phenomenon. The goal here is not to derive formulas for various relaxation mechanisms but rather to address the following questions:
- Relaxation as an ensemble-enabling process (thermo-dynamics)
- The role of relaxation in establishing nuclear magnetic [thermal] polarization
- Relaxation and phase coherence of quantum spin states
- Relaxation and the feasibility of a single-spin experiment
- Relaxation and the concept of "spontaneous" emission
- Time-dependent Hamiltonians, time-averaging, and the nature of quantum transitions
- Is an FID a superposition of instantaneous transitions or of lengthy transitions?
- Comparing CW and pulsed NMR in the limit of very long relaxation times
- Relaxation via coil-induced magnetic field fluctuations
- Relaxation and S/N ratio
The Author will present his personal opinions about these topics which, in some cases, do not match current paradigms, and in some cases are neither supported nor contradicted by any paradigm. The main goal of the presentation is simply to generate a lively discussion.