Orthorhombic and Trigonal Electron-Spin-Resonance Spectra ofCe3+Ions in CaF2

Two new electron-spin-resonance spectra, one having trigonal and the other having orthorhombic symmetry, have been observed in Ca${\mathrm{F}}_2$ doped with small amounts of Ce${\mathrm{O}}_2$. The $x$ and $y$ axes of the orthorhombic spectrum lie in the (110) plane and are tilted by an angle $\delta =13.8\mathrm{}\pm {0.2}^{\circ }$ from the [$\overline{1}10$] and the [001] axes, respectively, and the $z$ axis lies along the [110] axis. The components of the $g$ tensor for the two spectra are: orthorhombic, $g_x=0.844\mathrm{}\pm 0.001$, $g_y=0.22\mathrm{}\pm 0.05$, $g_z=3.286\mathrm{}\pm 0.001$; trigonal, $g_{\parallel }=3.673\mathrm{}\pm 0.0021$, $g_{\perp }\le 0.3$.