Infrared-absorption spectra of substitutional ${\mathrm{Cu}}^{2+}$ ions in ZnTe have been measured at 4.6 K. Several distinct absorption peaks are observed between 800 and 2000 ${\mathrm{cm}}^{\mathrm{-}1}$. Absorption peaks at 1002 and 1069 ${\mathrm{cm}}^{\mathrm{-}1}$ are identified as zero-phonon lines arising from ${}_{}{}^2{}_{}{}^{}$${\mathit{T}}_2$${\to }^2$E transitions. Between 1069 and 2000 ${\mathrm{cm}}^{\mathrm{-}1}$ several sets of sharp absorption lines are seen to recur regularly at an interval of 210 ${\mathrm{cm}}^{\mathrm{-}1}$, corresponding to the LO phonon energy. Within each set distinct vibronic sidebands that cannot be identified with critical-point energies of TA, LA, TO, or LO phonon modes are observed. A dynamic Jahn-Teller effect, involving coupling between a single-phonon mode and the electronic states of the ${}_{}{}^2{}_{}{}^{}$E level, is proposed to account for the observed spectra. The spectra are adequately described by a Jahn-Teller interaction in the linear-coupling approximation and by including only coupling to ε cluster modes. The observed first-order spin-orbit splitting in the ${}_{}{}^2{}_{}{}^{}$${\mathit{T}}_2$ state is much reduced from crystal-field-theory predictions and a dynamic Jahn-Teller interaction in the ground ${}_{}{}^2{}_{}{}^{}$${\mathit{T}}_2$ state is shown to account for this effect.

Close

PrevNext

View figure in article