Spin dynamics of the positive muon radicals in the presence of rapid electron spin exchange: frequency shift and relaxation

Abstract

The spin dynamics of the positive muon in a muonium-like radical has been investigated in the case where the unpaired electron of the radical undergoes rapid spin flip collisions. If the spin flip rate lambda SF is much faster than the hyperfine frequency of the radical, the behaviour of the muon spin is very similar to that of a positive muon in diamagnetic environments. The field dependence of the relaxation and frequency shift will provide a tool to distinguish experimentally the muon in a radical which behaves like a free positive muon from a genuine diamagnetic muon. The work can be applied to a variety of fields involving muonium and hydrogen, such as spin dynamic in the gas phase and the muonium-like (hydrogen-like) states in semiconductors. The case where the muon undergoes both spin flip and charge transfer collisions is also discussed.