Optical absorption dips caused by vibronic antiresonances in ZnSe: Ni and ZnSe:Ti

The optical absorption associated with the 3 T 1 - 1 T 2 transition in ZnSe:Ni has been measured at helium temperatures. There are some sharp lines followed by a continuum. The sharp lines are interpreted in terms of a dynamic Jahn-Teller splitting of the excited state. A number of absorption dips are superimposed on the absorption continuum. They are attributed to vibronic antiresonances involving the same electronic state, the interaction being between a lattice phonon sideband and a localized oscillation sideband of this state. Similar dips occur in the spectrum of ZnSe:Ti. Values of the resonance parameters are reported.