The Muon F–μ+–F Hydrogen Bond–like Complex

Muon spin rotation (μSR) and relaxation has been used to study the local magnetic structure of K3Fe5F15. A collinear F–μ+–F ʹʹhydrogen bond-like’’ symmetric double minimum type complex with a F...F distance of 2.8 A and a separation between the two minima of 0.8 Å has been found in the paramagnetic phase. The apparent central position of the muon seems to be the result of fast muon tunneling between two equivalent minima in the F–μ+–F bond.