Quenching of excitonic luminescence of alkaline earth fluorides excited by VUV harmonics of femtosecond laser

We studied fast luminescence of barium, calcium and strontium fluoride crystals in the excitonic emission region. For excitation we used high harmonics of Ti:sapphire laser generated in the rare gas cells with photon energies from 15 to 50 eV. The usage of 600 fs excitation pulses with 1 kHz repetition rate coupled with conventional registration system allows us to measure the luminescence decay curves in the wide time domain from 50 ps up to 1 ms. Decay curves demonstrate the strong deviations from single and/or two-exponential decay laws. The decay curve profiles depend both on excitation and emission photon energies. We attribute the subnanosecond component to the fast dissociation of exciton to the F–H pair at 300 K. The energy transfer from exciton to the F-center or another exciton also contributes to the non-exponential decay.