On the Way of Introducing Some Basic NMR Aspects: From the Classical and Naive Quantum Models to the Density-Operator Approach

Abstract

Three levels of theory for explaining the basic pulsed-NMR process are discussed, which use, respectively, classical dynamics, quantum mechanics at the undergraduate chemistry level, and quantum mechanics including the density-operator formalism. The meaning of some basic NMR concepts, such as spin precession or phase coherence, is examined within each model. The reason for considering only one circularly polarized component of radiation when describing pulsed NMR experiments is examined and found to be easy to understand by resorting to angular momentum conservation.