Direct observation of a diamagnetic product in gas-phase reactions of muonium by muon spin resonance

Direct observation of muonium reacting with uncapped gold nanoparticles in porous silica and nature of the final state

We report the reaction of muonium (Mu = [μ⁺e^-]), a light isotopic analog of hydrogen, with uncapped gold nanoparticles embedded in mesoporous silica. Using the radio-frequency muon spin rotation (RF-μSR) technique, we directly observe and characterize the resulting final state on the nanoparticle surface, showing conclusively its diamagnetic nature. The magnetic environment experienced by the reacted muons is only weakly perturbed compared to that of muons in a silica reference, consistent with the surface of the gold nanoparticles being metallic and non-magnetic. We demonstrate the potential of RF-μSR for the investigation of the surface properties of nanoparticles and show the feasibility of Knight shift measurements of muons on metal surfaces.

Rate constants for the slow Mu + propane abstraction reaction at 300 K by diamagnetic RF resonance

The rate constant for the slow Mu + propane abstraction reaction has been determined by diamagnetic RF resonance. The curves show simulations of the μSR resonance signal. This study provides an important new test of reaction rate theory for the alkanes.