The positive muon and μSR spectroscopy: powerful tools for investigating the structure and dynamics of free radicals and spin probes in complex systems

Abstract

The positive muon (μ⁺) can be incorporated into free radicals where it acts as a probe of the structure and dynamics. The muoniated radicals are characterized by a series of magnetic resonance techniques known as μSR for muon spin rotation, resonance and relaxation spectroscopy. In this review it is shown how μSR can be used to obtain information about the structure, dynamics, and local environments of transient radicals in solids like zeolites, in solution or even in exotic solvents like supercritical water. It will also be demonstrated that muoniated radicals can be used as probes in complex systems, such as rod-like and discotic liquid crystals, bilayers and polymers, where they have advantages over traditional spin labelling.