Electron Spin Resonance of Boron in Single—Crystal BeO

Single crystals of synthetic BeO which have been irradiated with 6‐MeV electrons show an ESR spectrum at room temperature identified as being due to boron ions substituting for beryllium at normal lattice sites. The hyperfine tensor A is cylindrically symmetric with its principal axis pointing towards one of the near oxygen bonds. Six equivalent directions are observed corresponding to the positions of the nonaxial nearest‐neighbor oxygen atoms. The constants of the spin Hamiltonian are: g∥ = 2.0035±0.0005, g⊥ = 2.0044±0.0005, A∥ = 122 Oe, A⊥ = 76.5 Oe. The spectrum is analyzed in terms of the paramagnetic electron occupying an antibonding orbital located along the direction of a B–O bond. Comparison of the observed hyperfine interaction with those expected for the free atom suggests deviations of the orbital from tetrahedral sp3 configuration to one in which the ratio of the p to s contribution increases from √3 to 2.64, implying that the B–O bond is lengthened along the direction in which the paramagnet...