THEORETICAL INVESTIGATION OF SUBPICOSECOND VIBRONIC DYNAMICS IN ALKALI-HALIDES

We present a theoretical analysis of a recent femtosecond experiment o n alkali halide F-centers [1]. In the experiment, subpicosecond dynami cs of an optically excited vibronic wave packet in alkali halide F-cen ters was investigated by a pump-probe technique using femtosecond lase r pulses. The temporal evolution of the wave packet leads to damped pe riodic oscillations of the sample transmission. These are interpreted as the A(1g)(Gamma(1)(+)) breathing modes of the surrounding octahedro n of cations associated with the electronic ground and excited states. It is shown that the vibrational modes of lower symmetry are responsi ble for the observed transient Jahn-Teller effect.