Luminescence of CsTaF6 Studied by VUV Spectroscopy

Broad-band luminescence with maximum at 3.35 eV has been revealed from new luminescence material CsTaF6 under VUV excitation. This luminescence was interpreted as emission of molecular type self-trapped excitons localized at the [Ta F 6]ˉ complexes. The energy of effective vibrational mode responsible for exciton-lattice coupling was determined to be equal to 45 meV (363 cm-1), which does not correspond to the energy of breathing mode of [Ta F 6]ˉ complex vibrations. The observed luminescence possesses thermal quenching with activation energy ∼58 meV.