Vibration-induced absorption (Bband) ofs2-configuration ions in alkali halides. II. Magnetic circular dichroism

The magnetic circular dichroism (MCD) spectra of the $B$ band of ${\mathrm{In}}^{+}$ centers (KCl: ${\mathrm{In}}^{+}$), ${\mathrm{Sn}}^{2+}$ centers (KI: ${\mathrm{Sn}}^{2+}$, KBr: ${\mathrm{Sn}}^{2+}$, KCl: ${\mathrm{Sn}}^{2+}$), and ${\mathrm{Tl}}^{+}$ centers (KCl: ${\mathrm{Tl}}^{+}$) have been measured at various temperatures and compared with a theoretical MCD line shape, which was calculated by Matsushima et al. A doublet-structured $B$ band of the ${\mathrm{In}}^{+}$ center, a triplet-structured $B$ band of the ${\mathrm{Sn}}^{2+}$ center, and a nonstructured $B$ band of the ${\mathrm{Tl}}^{+}$ center have been interpreted consistently as being due to the Jahn-Teller effect for the $B$ state. The coupling with the Jahn-Teller inactive $A_{1g}$ vibrational mode is found to be as important as the coupling with the $T_{2g}$ mode which gives rise to the splitting of the $B$ band predominantly. It is found, from the MCD line shape of ${\mathrm{In}}^{+}$, ${\mathrm{Sn}}^{2+}$, and ${\mathrm{Pb}}^{2+}$ centers, that the $B$ band of the ${\mathrm{In}}^{+}$ and ${\mathrm{Sn}}^{2+}$ centers penetrates into the $A$-band region considerably.