Decay time of 2.09 eV luminescence of S2--vacancy centers and their optical and thermal stability in NaCl : S-2 crystals

An investigation was carried out on decay time of the 2.09 eV emission of S 2--vacancy pair centers in NaCl crystals. When the crystal was excited by a pulsed 337 nm light from an Nz laser, the 2.09 eV yellow luminescence prin cipally decayed with the lifetime of 14.2 mu s at low temperatures, and exh ibited a weak thermal quenching with an activation energy of 51.3 meV above about 150 K. Such S2--vacancy pair centers responsible for the 2.09 eV lum inescence were thermally stable at room temperature, and not bleached even when exposed to ultraviolet lights below about 5 eV. Thus, the 2.09 eV emis sion center possibly can be used as a solid-state laser active center worki ng at room temperature.