LUMINESCENCE LINES DUE TO THE N=2 FREE EXCITON-STATE OF WANNIER SERIES IN KI CRYSTALS

A resonance luminescence line and its LO phonon side bands due to n = 2 free excitons in KI are studied. Main results of measurements; (1) the resonance luminescence line is located at 6.186 eV which corresponds closely to the peak position of the zero phonon absorption line due to n = 2 excitons, (2) the shape of the line is symmetric Lorentzian with 1.6 meV width, (3) the quantum yield is 1 × 10 -5, (4) the height of the potential barrier between the n = 2 free exciton state and self-trapped exciton states is 3.0 meV, (5) the self-trapping probability by a tunnel process through the potential barrier is 2 ×1011 sec-1 and (6) the scattering probability from the n = 2 free exciton state to the n = 1 free exciton state is 2 × 1011sec-1. Furthermore, it is concluded that so called σ(4.12eV) luminescence and π(3.31 eV) luminescence are emitted from the self-trapped exciton states due to the n = 2 exciton state. © 1979, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.