Faraday Rotation of Rare-Earth Ions in CaF2. II. Experiments

The complex rotatory power of several rare-earth ions in the Ca${\mathrm{F}}_2$ lattice has been observed. Measurements on anomalous rotatory dispersion and concomitant circular dichroism about some spectral lines in Ca${\mathrm{F}}_2$:${\mathrm{Nd}}^{3+}$ and Ca${\mathrm{F}}_2$:${\mathrm{Er}}^{3+}$ crystals agree well with the theory of the preceding paper. The rotatory power of ${\mathrm{Gd}}^{3+}$ in Ca${\mathrm{F}}_2$ in the visible range is very small. By contrast, the rotation in (${\mathrm{Eu}}^{2+}$, ${\mathrm{Eu}}^{3+}$) doped Ca${\mathrm{F}}_2$ crystals is very large and stems from the ${\mathrm{Eu}}^{2+}$ ions. The rotatory dispersion measurements show that the strong absorption lines and bands of ${\mathrm{Eu}}^{2+}$ in the visible region are responsible for the large optical rotatory power of ${\mathrm{Eu}}^{2+}$. ${\mathrm{Gd}}^{3+}$ and ${\mathrm{Eu}}^{2+}$ are isoelectronic in structure, but the difference in their optical spectra gives rise to a significant difference in their optical rotatory power. This assertion is supported by experimental observations.