FEMTOSECOND SPECTROSCOPIC STUDIES OF THE LATTICE-RELAXATION INITIATED BY INTERACTING ELECTRON-HOLE PAIRS UNDER RELAXATION IN ALKALI-HALIDES

Femtosecond time-resolved spectroscopic studies have been carried out to reveal the relaxation of free electron-hole pairs in KBr. We find that a hole is relaxed to a self-trapped hole with a delay of 10 ps. Two relaxation channels of an electron-hole pair are found: one lasts for 40 ps and leads competitively to a self-trapped exciton (STE) or an F-H pair; the other terminates within 6 ps, bypasses the STE, and leads to an F-H pair. The former channel is ascribed to the interplay between an electron and a self-trapped hole, while the latter demonstrates the dynamic interplay of an electron and a hole during their lattice relaxation.