INVESTIGATION OF LUMINESCENT MATERIALS UNDER ULTRAVIOLET EXCITATION-ENERGIES FROM 5 TO 25 EV

We have measured the absolute vacuum ultraviolet-to-visible conversion, or quantum efficiency (QE) of a number of phosphor systems for VUV excitation energies from 5 eV (250 nm) to 25 eV (50 nm). Our results demonstrate a QE greater than one in several of the samples studied, where a QE of one is equivalent to one visible photon emitted for every absorbed VUV photon. These results not only confirm the previous results obtained by Ilmas and Savikhina [1] but reveal details that they were unable to see due to experimental limitations. Our results also demonstrate the need to minimize loss mechanisms such as color centers, trapping levels, and surface defects. These loss mechanisms can easily dominate the photoluminescent process, preventing a phosphor which exhibits MPE processes from achieving a QE greater than one.