Negative muon hyperfine transition rate in aluminum

Abstract

The residual polarization of theF ⁻ hyperfine state ofμ ⁻²⁷Al has been investigated as a function of applied transverse magnetic field strength using standard TD-μ ⁻SR techniques. TheF ⁻ precession frequency is −0.2623(5) [theoretical value: −0.2622] times that of the free muon in the same field. The observed muon decay electron asymmetry in theF ⁻ state decreases with increasing magnetic field strength, due to initial precession in the opposite direction of theF ⁺ state, which most muon initially populate, followed by a rapid transition to theF ⁻ state. A fit of the data to this model indicates a transition rateR=41(9)μs⁻¹, in good agreement with theoretical predictions. This method can be used to determineR experimentally in other cases where it is too fast to be observed directly.