Stress and Zeeman spectra in bismuth-doped and undoped calcium oxide

Abstract

Vibrational series headed by zero-phonon lines have long been known in the absorption and emission spectra of bismuth-doped calcium oxide phosphors. Single crystals of undoped and bismuth-doped calcium oxide have been obtained, making possible Zeeman and uniaxial stress experiments on the zero-phonon lines. The absorption line in bismuth-doped calcium oxide at 4.2°K is at 367.02 nm (27239 cm-1) and is shown to be an electric dipole transition occurring at a centre of cubic symmetry. Using a pulsed magnetic field of 120 kG, a Lande g factor of 0.40 has been found for this transition. In the single crystals of undoped calcium oxide at 4.2 °K there is a zero-phonon absorption line at 355.74 nm (28102 cm-1). This is also observed in proton or neutron irradiated samples and has been found previously in additively coloured crystals. This absorption line has also been shown to be an electric dipole transition occurring at a centre of cubic symmetry, but here there is no detectable Zeeman splitting. These results are discussed with reference to the possible assignment of this line to the F centre.