Bond-centered muonium in diamond: Resolved nuclear hyperfine structure

The nuclear hyperfine structure of bond-centered muonium in ¹³C enriched diamond has been resolved using time-differential transverse-field muon spin rotation. The measured nearest-neighbor ¹³C hyperfine parameters are compared to theoretical values from a recent ab initio Hartree-Fock type cluster calculation. The ratios of the measured ¹³C hyperfine parameters and free atom values indicate that 92% of the unpaired electron spin density resides on the two nearest-neighbor atoms, in marked contrast with the situation for the analogous muonium center in Si.