μSR in polyacetylenes

In a series of μ+ experiments either at UT-MSL BOOM or at TRIUMF, we have found that the positive muon can create an interesting and systematic “after-effect” in the well-known organic semiconductor polymer polyacetylene, (CH)x or (CD)x: the localized unpaired electron at nearby carbon sites is produced in cis-polyacetylene, to form a muon radical; in trans-polyacetylene, the electron becomes mobile and takes “soliton”-like one dimensional rapid motion along the chain. Recently experiments were extended towards the following three directions: a) diffusion properties of the muon produced solition in trans-polyacetylene; b) the details of radical structure in cis-polyacetylene, and c) μSR experiments on I-doped polyacetylene. These works are reviewed along with the possible future perspectives.