ESR investigation of molecular ions in SrO

Electron-spin-resonance spectra from two distinct molecular ion centers have been observed in SrO. The dominant center, after electron irradiation at 77 K, is a -oriented molecular ion replacing an ${\mathrm{O}}^{2-}$ ion in an otherwise normal lattice. At 140 K, this center thermally decays while the concentration of a second center increases significantly. The second center is a similar molecular ion which is stabilized by an unidentified lattice defect located at a nearest-neighbor cation site. Near 160 K, this perturbed molecular ion center is reorienting rapidly about the perturbation thus causing its ESR spectrum to exhibit axial symmetry instead of the orthorhombic symmetry observed at 77 K. The perturbed center thermally decays at 190 K.