Splitting of electron paramagnetic resonance lines of lithium–oxygen centers in isotopically enriched single crystals

A significant narrowing of the electron paramagnetic resonance (EPR) and additional hyperfine structures of lithium–oxygen (Li–O) centers was observed in isotopically enriched 28Si single crystals. Unexpected splitting was found, reflecting the principal axis of the formally assigned trigonal g -tensors being tilted 3° from the 〈 111 〉 crystal axis, i.e., the g -tensor of the Li–O center actually has a monoclinic symmetry. Furthermore the splitting of the 7Li hyperfine lines into four components was observed at a temperature of 3.5 K.