Discovery ofFA(II)centers in KF

We report the discovery of $F_A\left(\mathrm{II}\right)$ centers in ${\mathrm{Na}}^{+}$-doped and in ${\mathrm{Li}}^{+}$-doped KF. Both absorption and emission spectra are given. The formation of the type-II center in KF:Na was unexpected on the basis of simple theory. Also, emission energies are surprisingly close to those of the same center type in KCl and RbCl.