Exciton interaction with impurity in barium fluoride crystals

Optical absorption excitation and emission of alkaline-earth fluoride crystals doped with impurities, which did not introduce a new absorption band up to 8 eV, were investigated. Comparison of emission of BaF2-LaF3, BaF2-KF and doubly doped BaF2-LaF3, KF shows that interstitial fluorines are not the main exciton suppressors as thought before.The two stages of exciton suppression on the plot of exciton intensity against impurity concentration were observed. The first stage has the interaction length near 130 Å, while the interaction lengths of second stage are 10-30 Å, depending on impurity.