|
Chapters:
|
MuSR /
MuonSites< The muon fate at implantation | Index | Muon interactions > Quite often the fate of the muon is not unique. A number of distinct final states may be obtained with different probabilities. These states may simply correspond to distinct interstitial sites, due to alternative chemical bonds. Sometimes different sites correspond also to very different electronic configurations, as it is the case for intrinsic semiconductors, where metastable antibonding positions can be occupied, e.g. in Si at low temperatures. In this respect the situation is more complex than it would be for any other chemical species at thermal equilibrium, both because of the epithermal energy that the muon initially possesses, and because of the short timescale over which it is observed. Muon locations may be made inequivalent when the direction of the ordered electron magnetic moment in a magnet distinguishes two otherwise equivalent sites, yielding a different dipolar field at each of them. The multiple sites are effectively accounted for by considering that the total asymmetry {$A$} of the full implanted muon ensemble is divided into the partial asymmetries of the {$n$} distict muon sites, according to: {$ A(t) =\sum_{j=1}^N A_j(t) $} where the initial partial asymmetry, {$A_j(0)=A p_j$}, may be written in terms of the stopping probability {$p_j$} at the {$j$}-th site (with {$\sum_j p_j=1$}). Often one refers to a muon spin polarization function {$P_j$} at each site: {$A_j(t)=A_j(0) P_j(t)$} < The muon fate at implantation | Index | Muon interactions > |