Optical Spectrum ofCo2+in the Cubic Crystalline Field of CaF2

The optical spectrum of ${\mathrm{Co}}^{2+}$ in Ca${\mathrm{F}}_2$ is analyzed. Absorption bands are found at 3 μ, 1.5 μ, and 550 mμ. These bands show fine structure. In addition there are weak and narrower bands at 19 220, 19 580, 20 450, 21 750, 22 000, and 25 750 ${\mathrm{cm}}^{-1\mathrm{}}$, and intense lines at 44 250 and 48 200 ${\mathrm{cm}}^{-1\mathrm{}}$. The spectrum is interpreted to arise from transitions from the orbital singlet to various Stark levels split by spin-orbit interaction, and yields values of $Dq=340\mathrm{}\pm 10$ ${\mathrm{cm}}^{-1\mathrm{}}$, $E\left(P\right)=14\mathrm{}000\pm 100$ ${\mathrm{cm}}^{-1\mathrm{}}$, and $E\left(G\right)=16\mathrm{}250\pm 100$ ${\mathrm{cm}}^{-1\mathrm{}}$. The spectrum of ${\mathrm{Co}}^{2+}$ in the eight coordinated cubic symmetry is compared with ${\mathrm{Co}}^{2+}$ in octahedral and tetrahedral symmetry as well as with ${\mathrm{Cr}}^{3+}$ in octahedral symmetry.